A graded opening double-disc flat gate valve and its sealing pressure ratio adjustment method

Abstract

The present invention discloses a stepped-opening double-disc flat gate valve and a sealing pressure regulating method thereof. The flat gate valve comprises a valve body, a piston plate disposed in a central cavity formed between the valve body and a valve cover, the piston plate dividing the central cavity into an upper central cavity and a lower central cavity, and a cavity pressure regulating mechanism disposed on the piston plate; a center plate disposed at the lower end of a valve stem, left and right disc springs disposed between the center plate and left and right gate plates, respectively, and the center plate and the left and right gate plates cooperate in a stepped lifting manner; a channel connected to an outlet cavity is disposed at the bottom of the valve body, the lower central cavity can be connected to the channel via the gate plate partition cavity, a sealing plug is disposed at the lower end of the center plate, and the sealing plug cooperates with the channel; a sealing pressure regulating method is provided, wherein the cavity pressure regulating mechanism is used to regulate the medium pressure in the lower central cavity, thereby regulating the force exerted by the medium in the lower central cavity on the left and right gate plates, thereby regulating the sealing pressure of the sealing pairs between the left and right gate plates and the left and right valve seats, respectively. The present invention achieves gate sealing pressure regulation, thereby reducing leakage; and the gate opens in stages, thereby reducing wear.

Description

Technical Field

[0001] The present invention relates to an improved invention of a flat gate valve, in particular to an improved invention of a stepped-opening double-disc flat gate valve and a sealing pressure ratio regulating method thereof. Background Art

[0002] A double-disc flat gate valve has two discs within the valve body. Compared to a single-disc flat gate valve, it can withstand greater shutoff pressure and flow, and can be used in high-pressure, high-temperature, and high-flow pipelines. Double-disc flat gate valves offer flexibility and can be used in most operating conditions. They are also leak-resistant and offer excellent sealing performance. However, their disadvantages are that when the valve is closed, the sealing pressure ratio of the sealing pair between the valve seat and the disc cannot be controlled. When the sealing pressure ratio of the sealing pair is too high, the torque required to open it is large, and the sealing pair is susceptible to wear. When the sealing pressure ratio of the sealing pair is too low, although the torque required to open it is small and the sealing pair is less susceptible to wear, leakage is more likely to occur. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a graded opening double-disc flat gate valve and a sealing pressure ratio adjustment method thereof.

[0004] In order to solve the above technical problems, the present invention is implemented by adopting the following technical solutions: this type of graded opening double-gate flat gate valve includes a valve body, a valve cover, a valve stem, a left gate plate, a right gate plate, a left valve seat and a right valve seat, the valve body includes an inlet cavity and an outlet cavity, the left gate plate is sealed with the left valve seat, and the right gate plate is sealed with the right valve seat, the valve cover is arranged on the upper end of the valve body, the valve stem can be lifted and lowered and is arranged on the valve cover, and the upper end of the valve stem is equipped with a lifting mechanism, which is characterized in that a piston plate that can be lifted and lowered is provided in the middle cavity formed between the valve body and the valve cover, the piston plate divides the middle cavity into an upper middle cavity and a lower middle cavity, and a cavity pressure regulating mechanism is provided on the piston plate, the valve stem seal passes through the piston plate, the piston plate is driven to lift and lower by the valve stem, and can be slid relative to it, and the corresponding valve stem is provided with a driving step located above and below the piston plate. and a limit block; a center plate is provided at the lower end of the valve stem, and the center plate is limited in the gate plate compartment between the left gate plate and the right gate plate, and a left disc spring and a right disc spring are respectively provided between the center plate and the left gate plate and the right gate plate, and a left lifting groove and a right lifting groove are also provided on both sides of the center plate, and a relative left lifting block and a right lifting block are provided on the inner side surfaces of the corresponding left gate plate and the right gate plate. The left lifting block is located in the left lifting groove and drives it, and a left spring is provided between the upper end of the left lifting block and the top of the left lifting groove, and the right lifting block is located in the right lifting groove and drives it, and a right spring is provided between the upper end of the right lifting block and the top of the right lifting groove, and the bottom surface of the left lifting groove is higher than the bottom surface of the right lifting groove; a channel connecting to the outlet cavity is provided at the bottom of the valve body, and the lower middle cavity can be connected to the channel through the gate plate compartment. A sealing plug is provided at the lower end of the center plate, and the sealing plug can be moved into the channel to seal with it.

[0005] The cavity pressure regulating mechanism includes a pressure relief structure and a check structure arranged on the piston plate, and the preset opening pressure of the pressure relief structure is adjustable. The medium in the upper middle cavity can enter the lower middle cavity through the check structure, and the medium in the lower middle cavity can enter the upper middle cavity through the pressure relief structure.

[0006] The pressure relief structure includes a liquid inlet hole, a pressure relief flap, an adjusting spring, an adjusting sleeve and a polygonal rod. The adjusting sleeve is threadedly connected and embedded in the upper part of the piston plate. The pressure relief flap is arranged at the lower port of the adjusting sleeve. A guide hole is reserved between the pressure relief flap and the inner wall of the adjusting sleeve. An adjusting spring is arranged between the pressure relief flap and the top of the adjusting sleeve. A pressure relief hole is arranged on the upper part of the adjusting sleeve. A liquid inlet hole is arranged at the lower part of the piston plate, and the liquid inlet hole and the pressure relief flap are sealed together. A straight gear rod is elastically raised and lowered on the valve cover, a polygonal hole is provided at the lower end of the straight gear rod, a polygonal rod is arranged in the polygonal hole, and the lower end of the polygonal rod is connected to the adjusting sleeve. A worm is rotatably passed through the valve cover, and the worm is meshed with the straight gear rod.

[0007] The valve body is provided with a left guide groove and a right guide groove for assisting the left gate plate and the right gate plate in lifting and lowering, and the bottom of the valve body is provided with a left lower top block and a right lower top block for limiting the left gate plate and the right gate plate.

[0008] The upper end surface of the driving step of the valve stem is provided with a stem upper sealing surface, and the corresponding valve cover is provided with a cover upper sealing surface which seals with the stem upper sealing surface.

[0009] The left lifting block is provided with a left ferrule, and the right lifting block is provided with a right ferrule.

[0010] The channel comprises a lower hole and a side hole which are connected to each other, and the lower hole is for the sealing plug to extend into.

[0011] A telescopic cavity is provided on the valve cover corresponding to the spur gear rod, and the upper end of the spur gear rod is connected to the telescopic cavity through an upper return spring.

[0012] The lower end surface of the valve cover is limitedly matched with the upper end surface of the piston plate, and the valve cover forms the upper limit of the piston plate.

[0013] The sealing pressure ratio adjustment method of the flat gate valve is to adjust the medium pressure in the lower middle cavity through the cavity pressure adjustment mechanism to adjust the force of the medium in the lower middle cavity on the left and right gate plates, thereby adjusting the sealing pressure ratio of the sealing pair between the left and right gate plates and the left and right valve seats respectively.

[0014] The beneficial effects of the present invention are an improved graded opening double-disc flat gate valve and a sealing pressure ratio regulation method thereof. The valve utilizes a cavity pressure regulation mechanism to regulate the medium pressure in the lower middle cavity when the valve is in a closed state, thereby adding an additional force to the sealing pair between the valve seat and the gate, thereby increasing the sealing pressure ratio of the sealing pair and enhancing the sealing performance. When the valve needs to be opened, a graded opening method is utilized to reduce the sealing pressure ratio of the sealing pair between the valve seat and the gate, resulting in a small opening torque, small wear on the sealing surface, and a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0016] Figure 1 This is a schematic diagram of the gate valve in the closed state of the present invention;

[0017] Figure 2 This is a schematic diagram of the gate valve of the present invention in an open state;

[0018] Figure 3 Schematic diagram of the gate plate of the gate valve in the closed state of the present invention;

[0019] Figure 4 It is a schematic diagram of the pressure relief structure of the present invention. DETAILED DESCRIPTION

[0020] The accompanying drawings show the structure of the present invention, and the following further describes its relevant details in conjunction with the accompanying drawings. Figure 1-4The stepped opening double-disc flat gate valve comprises a valve body 1, a valve cover 14, a valve stem 15, a left gate plate 42, a right gate plate 56, a left valve seat 4 and a right valve seat 33. The valve body 1 comprises an inlet cavity 2 and an outlet cavity 32. The left gate plate 42 is sealed with the left valve seat 4, and the right gate plate 56 is sealed with the right valve seat 33. The valve cover 14 is covered on the upper end of the valve body 1. The valve stem 15 can be lifted and lowered through the valve cover 14, and a packing 26 is provided between the valve stem 15 and the upper end of the valve cover 14. The packing 26 is pressed by the pressure cover 25, and the pressure cover 25 is fixed to the top of the valve cover 14 by adjusting the fastener 24. The upper end of the valve stem 15 is equipped with a lifting mechanism, which comprises a bracket 17, a large handwheel 19, a screw sleeve 23, a plane bearing 22 and a screw 18. The screw The rod 18 is connected to the upper end of the valve stem 15, and the screw sleeve 23 is threadedly engaged with the screw 18. The screw sleeve 23 is rotatably arranged in the bracket 17 through a plane bearing 22, and the upper end of the screw sleeve 23 is driven by a large handwheel 19. The upper end of the screw 18 passes through the large handwheel 19 and is equipped with a protective cover 20. The protective cover 20 is provided with a longitudinally arranged observation window, and the corresponding upper end of the screw 18 is provided with an indicator block 21 to display the lifting and lowering of the valve stem 15; a piston plate 6 that can be lifted and lowered is provided in the middle cavity formed between the valve body 1 and the valve cover 14, and a sealing ring 7 is provided on the outer periphery of the piston plate 6, and is sealed and slidably matched with the inner wall of the middle cavity. The piston plate 6 divides the middle cavity into an upper middle cavity 28 and a lower middle cavity 31, and a cavity pressure regulating mechanism is provided on the piston plate 6. The valve stem 15 seals and passes through the piston plate 6. The piston plate 6 is driven to rise and fall by the valve stem 15 and can be slid relative to it. The corresponding valve stem 15 is provided with a driving step 3 and a limit block 5 located above and below the piston plate 6. The interval between the driving step 3 and the limit block 5 is greater than the thickness of the piston plate 6, so that the piston plate 6 can slide relative to the valve stem 15 to achieve delayed driving; the lower end of the valve stem 15 is provided with a center plate 45, and the center plate 45 is limited in the gate compartment between the left gate plate 42 and the right gate plate 56, and a left disc spring 43 and a right disc spring 55 are respectively provided between the center plate 45 and the left gate plate 42 and the right gate plate 56. The corresponding center plate 45 is provided with a left disc spring groove 44 and a right disc spring groove 54, for installing the left disc spring 43 and the right disc spring 55 respectively, and a left lifting groove is also provided on both sides of the center plate 45 48 and the right lifting groove 51, the corresponding left gate plate 42 and the right gate plate 56 are provided with a relative left lifting block 67 and a right lifting block 68 on the inner side surface, the left lifting block 67 and the right lifting block 68 are at the same height, the left lifting block 67 is located in the left lifting groove 48 and is driven to cooperate therewith, there is a relative movement interval between the left lifting block 67 and the left lifting groove 48, and a left spring 49 is provided between the upper end of the left lifting block 67 and the top of the left lifting groove 48, the right lifting block 68 is located in the right lifting groove 51 and is driven to cooperate therewith, there is a relative movement interval between the right lifting block 68 and the right lifting groove 51, and a right spring 50 is provided between the upper end of the right lifting block 68 and the top of the right lifting groove 51, the left lifting groove bottom surface 46 is higher than the right lifting groove bottom surface 53, then the left gate plate 42 is lifted before the right gate plate 56;The bottom of the valve body 1 is provided with a passage 38 that connects to the outlet chamber 32. The lower middle chamber 31 can be connected to the passage 38 through the gate partition. A sealing plug 58 is provided at the lower end of the center plate 45. The sealing plug 58 can be moved into the passage 38 to seal it. The sealing plug 58 is fixed to the switching rod 57 by a positioning screw 59. The switching rod 57 is fixed to the lower end of the center plate 45.

[0021] As a further improved specific embodiment, the cavity pressure regulating mechanism includes a pressure relief structure 8 and a check structure 30 arranged on the piston plate 6, and the preset opening pressure of the pressure relief structure 8 is adjustable. The medium in the upper middle cavity 28 can enter the lower middle cavity 31 through the check structure 30, and the medium in the lower middle cavity 31 can enter the upper middle cavity 28 through the pressure relief structure 8.

[0022] As a further improved specific embodiment, the pressure relief structure 8 includes a liquid inlet hole 60, a pressure relief flap 61, an adjusting spring 64, an adjusting sleeve 66 and a polygonal rod 9, the adjusting sleeve 66 is threadedly connected and embedded in the upper part of the piston plate 6, the pressure relief flap 61 is arranged at the lower port of the adjusting sleeve 66, a guide hole 62 is reserved between the pressure relief flap 61 and the inner wall of the adjusting sleeve 66, an adjusting spring 64 is provided between the pressure relief flap 61 and the top of the adjusting sleeve 66, a pressure relief hole 65 is provided on the upper part of the adjusting sleeve 66, and the lower part of the piston plate 6 is provided with a liquid inlet hole 60, a liquid inlet hole 60 is sealed with the pressure relief flap 61; the valve cover 14 is elastically raised and lowered with a straight gear rod 11, the lower end of the straight gear rod 11 is provided with a polygonal hole 10, the polygonal hole 10 is equipped with a polygonal rod 9, the lower end of the polygonal rod 9 is connected to the adjusting sleeve 66, and the valve cover 14 is rotatably penetrated by a worm 13, the worm 13 is engaged with the straight gear rod 11, and the outer end of the worm 13 is connected to a small handwheel 12. Determined by the characteristics of the worm 13 and the straight gear rod 11, the worm 13 can drive the straight gear rod 11 to rotate, and the straight gear rod 11 cannot transmit the worm 13 when it is raised or lowered.

[0023] As a further improved specific implementation method, the valve body 1 is equipped with a left guide groove 40 and a right guide groove 41 to assist the left gate plate 42 and the right gate plate 56 in lifting and lowering, so that they can lift and lower stably. The bottom of the valve body 1 is equipped with a left lower top block 39 and a right lower top block 35 to limit the left gate plate 42 and the right gate plate 56, so as to limit the left gate plate 42 and the right gate plate 56 from moving down into place.

[0024] As a further improved specific implementation, the upper end surface of the driving step of the valve stem 15 is provided with a stem upper sealing surface 29, and the corresponding valve cover 14 is provided with a cover upper sealing surface 27 that seals with it.

[0025] As a further improved specific implementation method, a left ring 47 is provided on the left lifting block 67, and a right ring 52 is provided on the right lifting block 68. The left ring 47 buffers and reduces wear between the left lifting block 67 and the left lifting groove 48, and the right ring 52 buffers and reduces wear between the right lifting block 68 and the right lifting groove 51.

[0026] As a further improved embodiment, the passage 38 includes a connected lower hole 36 and a side hole 34. The lower hole 36 corresponds to the gate compartment and the sealing plug 58. The lower hole 36 is for the sealing plug 58 to extend into. The side hole 34 connects the lower end of the lower hole 36 with the outlet chamber 32. The valve body 1 corresponding to the lower hole 36 is provided with an inspection port for the sealing plug 58 and is equipped with a lower screw plug 37.

[0027] As a further improved specific implementation, a telescopic cavity is provided on the valve cover 14 corresponding to the spur rod 11 , and the upper end of the spur rod 11 is connected to the telescopic cavity through an upper return spring 16 to achieve elastic lifting of the spur rod 11 .

[0028] As a further improved specific implementation, the lower end surface of the valve cover 14 is limitedly matched with the upper end surface of the piston plate 6 , and the valve cover 14 forms the upper limit of the piston plate 6 .

[0029] The opening process of the present invention:

[0030] Rotate the large handwheel 19 to drive the screw sleeve 23 to rotate. Since a threaded connection is formed between the screw sleeve 23 and the screw rod 18, the screw rod 18 and the valve stem 15 are driven to move upward, and then the center plate 45 and the sealing plug 58 are driven to move upward. When the sealing plug 58 is separated from the channel 38, the lower middle cavity 31 is connected to the channel 38. The medium in the lower middle cavity 31 enters the outlet cavity 32 through the gate compartment and the channel 38 in turn. The pressure of the medium in the lower middle cavity 31 decreases, and the sealing pressure ratio of the sealing pair between the left valve seat 4 and the left gate plate 42 decreases. When the bottom surface 46 of the left lifting groove 48 contacts the left ring 47, the upward-moving valve stem 15 and the center plate 45 drive the left gate plate 42 to move upward. , the sealing pair friction between the left valve seat 4 and the left gate plate 42 is small, the sealing pair wear is small, and the opening torque is small; as the left valve seat 4 opens, the medium entering the outlet cavity 32 increases, and the sealing specific pressure of the sealing pair between the right valve seat 33 and the right gate plate 56 decreases; as the valve stem 15 and the center plate 45 continue to move upward, when the bottom surface of the right lifting groove 51 contacts the right ring 52, the upward-moving valve stem 15 and the center plate 45 drive the right gate plate 56 to move upward, the sealing pair friction between the right valve seat 33 and the right gate plate 56 is small, the sealing pair wear is small, and the opening torque is also small, the right gate plate 56 opens, the medium in the inlet cavity 2 enters the outlet cavity 32, and the valve opens;

[0031] As the medium from inlet chamber 2 enters lower middle chamber 31, piston plate 6, propelled by the medium in lower middle chamber 31 and driven by valve stem 15, moves upward until the upper end face of piston plate 6 presses against the lower end face of valve cover 14. At this point, the valve is fully open, and the upper sealing surface 29 in the middle of valve stem 15 presses against the upper sealing surface 27 of the valve cover, preventing the medium in upper middle chamber 28 from impacting packing 26 and, in turn, from leaking out through packing 26. As piston plate 6 drives pressure relief structure 8 and spur gear 11 upward, due to the spur teeth on the exterior of spur gear 11, the upward movement of spur gear 11 does not cause rotation of worm gear 13.

[0032] The closing process of the present invention:

[0033] Rotate the large handwheel 19 in the opposite direction to drive the screw sleeve 23 to rotate in the opposite direction. Since the screw sleeve 23 and the screw rod 18 are threadedly connected, the screw rod 18 and the valve stem 15 are driven downward, and then the center plate 45, the piston plate 6 and the sealing plug 58 are driven downward. Since the left and right rings 47, 52 are pressed against the bottom 46, 53 of the left and right lifting grooves by the left and right springs 49, 50 respectively, the left and right gate plates 42, 56 are driven downward together at the same time. Under the action of the left and right guide grooves 40, 41 and the left and right disc springs 43, 55, the left and right gate plates 42, 56 press the left and right valve seats 4, 33 respectively. When the lower end surface of the right gate plate 56 contacts the right lower top block 35, the right gate plate 56 stops moving downward, the center plate 45 continues to move downward, the right spring 50 continues to be compressed, and the left gate plate 42 continues to move downward with the center plate 45. When the lower end surface of the left gate plate 42 contacts the left lower top block 39, the left gate plate 42 stops moving downward, the center plate 45 continues to move downward, and the sealing plug 58 continues to move downward with the center plate 45 until the sealing plug 58 enters the channel 38 and forms a seal with the channel 38. The lower middle cavity 31 is isolated from the channel 38, and the medium in the lower middle cavity 31 cannot continue to enter the outlet cavity 32 through the gate partition cavity and the channel 38.

[0034] At this time, continue to rotate the large handwheel 19, driving the center plate 45, piston plate 6 and sealing plug 58 to move downward. During the downward movement of the piston plate 6, the volume of the lower middle chamber 31 decreases, and the medium in the lower middle chamber 31 is subjected to pressure, thereby increasing the pressure of the medium in the lower middle chamber 31. The medium in the lower middle chamber 31 acts on the left and right gate plates 42 and 56, respectively, and the force of pressing against the left and right valve seats 4 and 33 increases. The sealing pressure ratio of the sealing pair between the left and right gate plates 42 and 56 and the left and right valve seats 4 and 33 increases, and the sealing between the left and right gate plates 42 and 56 and the left and right valve seats 4 and 33 is enhanced, which further enhances the sealing performance of the valve. During the downward movement of the pressure relief structure 8 driven by the piston plate 6, since the straight tooth rod 11 is provided with straight teeth on the outside, the straight tooth rod 11 will not drive the worm 13 to rotate when it moves downward together with the pressure relief structure 8 under the action of the upper return spring 16.

[0035] The sealing pressure ratio adjustment method of the flat gate valve of the present invention adjusts the medium pressure in the lower middle cavity 31 through the cavity pressure adjustment mechanism to adjust the force of the medium in the lower middle cavity 31 on the left and right gate plates 42 and 56, thereby adjusting the sealing pressure ratio of the sealing pair between the left and right gate plates 42 and 56 and the left and right valve seats 4 and 33 respectively.

[0036] Assuming that there is no medium pressure in the lower middle cavity 31, the force required for the sealing specific pressure of the sealing pair between the left and right gate plates 42, 56 and the left and right valve seats 4, 33 respectively is provided by the left and right butterfly springs respectively. However, the medium pressure in the pipeline may change. When the medium pressure in the pipeline is low, the sealing specific pressure required by the sealing pair is small, that is, the force required by the left and right butterfly springs acting on the left and right gate plates 42, 56 respectively is small; when the medium pressure in the pipeline is high, the sealing specific pressure required by the sealing pair is large, that is, the force required by the left and right butterfly springs acting on the left and right gate plates 42, 56 respectively is large; however, when the valve is installed on the pipeline, the left and right butterfly springs cannot be replaced, resulting in a narrow range of use of the valve.

[0037] Method for regulating the medium pressure in the lower middle cavity 31:

[0038] When the left and right gate plates 42 and 56 are in the closed state, rotate the large handwheel 19 to drive the valve stem 15, piston plate 6, center plate 45 and sealing plug 58 to continue to move downward, and observe the leakage of the outlet chamber 32. If there is medium leakage, reverse the small handwheel 12 to drive the worm 13 to rotate, and then drive the straight gear rod 11 to rotate around its own axis. Due to the cooperation between the polygonal rod 9 and the polygonal hole 10, the adjusting sleeve 66 is driven to rotate. The adjusting sleeve 66 is installed on the piston plate 6 by a threaded connection. The adjusting sleeve 66 rotates downward, the adjusting spring 64 is compressed, and the downward force of the adjusting spring 64 on the pressure relief flap 61 increases, and the preset opening pressure of the pressure relief structure 8 increases.

[0039] The preset opening pressure means that: when the medium pressure at the liquid inlet hole 60 is equal to the preset opening pressure, the downward force of the regulating spring 64 on the pressure relief flap 61 is balanced by the upward force of the medium at the liquid inlet hole 60 on the pressure relief flap 61; when the medium pressure at the liquid inlet hole 60 is greater than the preset opening pressure, the upward force of the medium at the liquid inlet hole 60 on the pressure relief flap 61 is greater than the downward force of the regulating spring 64 on the pressure relief flap 61, the pressure relief flap 61 moves upward, the pressure relief structure 8 opens, and the medium in the lower middle cavity 31 enters the upper middle cavity 28 through the liquid inlet hole 60, the guide hole 62, the pressure relief cavity 63, and the pressure relief hole 65 in sequence; when the medium pressure at the liquid inlet hole 60 is less than the preset opening pressure, the liquid inlet hole 60 opens. The upward force of the medium acting on the pressure relief flap 61 is less than the downward force of the adjusting spring 64 acting on the pressure relief flap 61. The pressure relief flap 61 moves downward, the pressure relief structure 8 is closed, and the medium in the lower middle cavity 31 no longer continues to enter the upper middle cavity 28. The lower middle cavity 31 can withstand a higher medium pressure. When the piston plate 6 moves downward with the valve stem 15, the lower middle cavity 31 continues to be compressed. The medium pressure in the lower middle cavity 31 continues to rise when it does not reach the preset opening pressure. The sealing specific pressure of the sealing pair between the left and right gate plates 42 and 56 and the left and right valve seats 4 and 33 respectively continues to increase. Continue to observe the leakage of the outlet cavity 32. If there is still medium leakage, repeat the above steps until no medium leakage is observed at the outlet cavity 32.

[0040] The check structure 30 is a one-way valve. During the opening or closing process of the valve, when the medium pressure in the upper middle chamber 28 is greater than the medium pressure in the lower middle chamber 31, the medium in the upper middle chamber 28 enters the lower middle chamber 31 through the check structure 30, ensuring that the medium pressure in the upper middle chamber 28 is less than or equal to the medium pressure in the lower middle chamber 31.

[0041] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A stepped-opening double-disc flat gate valve, comprising a valve body, a valve cover, a valve stem, a left gate, a right gate, a left valve seat, and a right valve seat. The valve body comprises an inlet cavity and an outlet cavity. The left gate seals with the left valve seat, and the right gate seals with the right valve seat. The valve cover is disposed on the upper end of the valve body. The valve stem is liftably disposed on the valve cover. A lifting mechanism is provided on the upper end of the valve stem. The valve body is characterized in that: A piston plate that can be raised and lowered is provided in the middle cavity formed between the valve body and the valve cover. The piston plate divides the middle cavity into an upper middle cavity and a lower middle cavity, and a cavity pressure regulating mechanism is provided on the piston plate. The valve stem seal passes through the piston plate, and the piston plate is driven to rise and fall by the valve stem and can slide relative to it. The corresponding valve stem is provided with a driving step and a limit block located above and below the piston plate; a center plate is provided at the lower end of the valve stem, and the center plate is limited in the gate cavity between the left and right gate plates, and left and right disc springs are provided between the center plate and the left and right gate plates respectively, and left and right disc springs are also provided on both sides of the center plate. Lifting groove, corresponding left and right gate plates are provided with relative left and right lifting blocks on their inner sides, the left lifting block is located in the left lifting groove and is driven to cooperate with it, and a left spring is provided between the upper end of the left lifting block and the top of the left lifting groove, the right lifting block is located in the right lifting groove and is driven to cooperate with it, and a right spring is provided between the upper end of the right lifting block and the top of the right lifting groove, the bottom surface of the left lifting groove is higher than the bottom surface of the right lifting groove; the bottom of the valve body is provided with a channel connected to the outlet cavity, the lower middle cavity can be connected to the channel through the gate plate partition cavity, and a sealing plug is provided at the lower end of the center plate, which can be moved into the channel to seal with it; The cavity pressure regulating mechanism includes a pressure relief structure and a check structure arranged on the piston plate, and the preset opening pressure of the pressure relief structure is adjustable. The medium in the upper middle cavity can enter the lower middle cavity through the check structure, and the medium in the lower middle cavity can enter the upper middle cavity through the pressure relief structure.

2. The staged opening double-disc flat gate valve according to claim 1, characterized in that: The pressure relief structure includes a liquid inlet hole, a pressure relief flap, an adjusting spring, an adjusting sleeve and a polygonal rod. The adjusting sleeve is threadedly connected and embedded in the upper part of the piston plate. The pressure relief flap is arranged at the lower port of the adjusting sleeve. A guide hole is reserved between the pressure relief flap and the inner wall of the adjusting sleeve. An adjusting spring is arranged between the pressure relief flap and the top of the adjusting sleeve. A pressure relief hole is arranged on the upper part of the adjusting sleeve. A liquid inlet hole is arranged at the lower part of the piston plate, and the liquid inlet hole and the pressure relief flap are sealed together. A straight gear rod is elastically raised and lowered on the valve cover, a polygonal hole is provided at the lower end of the straight gear rod, a polygonal rod is arranged in the polygonal hole, and the lower end of the polygonal rod is connected to the adjusting sleeve. A worm is rotatably passed through the valve cover, and the worm is meshed with the straight gear rod.

3. The staged opening double-disc flat gate valve according to claim 1, characterized in that: The valve body is provided with a left guide groove and a right guide groove for assisting the left gate plate and the right gate plate in lifting and lowering, and the bottom of the valve body is provided with a left lower top block and a right lower top block for limiting the left gate plate and the right gate plate.

4. The step-by-step opening double-disc flat gate valve according to claim 1, characterized in that: The upper end surface of the driving step of the valve stem is provided with a stem upper sealing surface, and the corresponding valve cover is provided with a cover upper sealing surface which seals with the stem upper sealing surface.

5. The staged opening double-disc flat gate valve according to claim 1, characterized in that: The left lifting block is provided with a left ferrule, and the right lifting block is provided with a right ferrule.

6. The staged opening double-disc flat gate valve according to claim 1, characterized in that: The channel comprises a lower hole and a side hole which are connected to each other, and the lower hole is for the sealing plug to extend into.

7. The staged opening double-disc flat gate valve according to claim 2, characterized in that: A telescopic cavity is provided on the valve cover corresponding to the spur gear rod, and the upper end of the spur gear rod is connected to the telescopic cavity through an upper return spring.

8. The staged opening double-disc flat gate valve according to claim 1, characterized in that: The lower end surface of the valve cover is limitedly matched with the upper end surface of the piston plate, and the valve cover forms the upper limit of the piston plate.

9. A method for regulating the sealing pressure ratio of a staged double-disc flat gate valve according to claim 1, characterized in that: The medium pressure in the lower middle cavity is adjusted by the cavity pressure regulating mechanism to adjust the force of the medium in the lower middle cavity on the left and right gate plates, thereby adjusting the sealing specific pressure of the sealing pair between the left and right gate plates and the left and right valve seats respectively.

Images