Staged opening type double-gate-plate flat gate valve and sealing specific pressure adjusting method thereof

Abstract

The invention discloses a staged opening double-disc flat gate valve and a sealing specific pressure adjusting method thereof, the flat gate valve comprises a valve body, a piston plate is arranged in a middle cavity formed between the valve body and a valve cover, the piston plate divides the middle cavity into an upper middle cavity and a lower middle cavity, and a cavity pressure adjusting mechanism is arranged on the piston plate; a center plate is arranged at the lower end of the valve rod, left and right disc springs are respectively arranged between the center plate and the left and right flashboards, and the center plate is in graded lifting fit with the left and right flashboards; a hole channel communicated with the outlet cavity is formed in the bottom of the valve body, the lower middle cavity can be communicated with the hole channel through the flashboard separation cavity, and a sealing plug is arranged at the lower end of the center plate and matched with the hole channel; according to the sealing specific pressure adjusting method, the medium pressure in the lower middle cavity is adjusted through the cavity pressure adjusting mechanism so as to adjust the acting force of the medium in the lower middle cavity on the left gate plate and the right gate plate, and therefore the sealing specific pressure of the sealing pairs between the left gate plate and the left valve seat and between the right gate plate and the right valve seat is adjusted. Adjustment of the gate sealing specific pressure is achieved, and leakage is reduced; the gate is opened in a staged mode, and abrasion is reduced.

Description

Technical Field

[0001] The present invention relates to an improved invention of a flat gate valve, and particularly to an improved invention of a stepped-opening double gate flat gate valve and a method for adjusting its sealing specific pressure. Background Art

[0002] A double gate flat gate valve refers to a valve body with two gate plates. Compared with a single gate flat gate valve, it can withstand greater cutting pressure and flow rate, and can be used in high-pressure, high-temperature, and large-flow pipelines. The double gate flat gate valve has strong flexibility, can be used under most working conditions, and is not easy to leak, with good valve sealing performance. Its disadvantages are as follows: when the valve is closed, the sealing specific pressure of the sealing pair between the valve seat and the gate plate cannot be controlled. When the sealing specific pressure of the sealing pair is too large, the opening torque required is large, and the sealing pair is easily worn; when the sealing specific pressure of the sealing pair is too small, although the opening torque required is small and the sealing pair is not easily worn, leakage is 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 stepped-opening double gate flat gate valve and a method for adjusting its sealing specific pressure.

[0004] To solve the above technical problem, the present invention is implemented by adopting the following technical solution: This stepped-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 sealingly matched with the left valve seat, and the right gate plate is sealingly matched with the right valve seat. The valve cover is provided on the upper end of the valve body. The valve stem is vertically penetratable through the valve cover, and a lifting mechanism is provided at the upper end of the valve stem. It is characterized in that: A liftable piston plate 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 adjustment mechanism is provided on the piston plate. The valve stem penetrates through the piston plate in a sealed manner. The piston plate is driven by the valve stem to lift and can be slidably arranged relative to it. Correspondingly, driving steps and limit blocks are provided on the valve stem above and below the piston plate. A central plate is provided at the lower end of the valve stem. The central plate is limited in the gate plate partition cavity between the left gate plate and the right gate plate. Left and right disc springs are respectively provided between the central plate and the left gate plate and the right gate plate. Left and right lifting grooves are further provided on both sides of the central plate. Correspondingly, left and right lifting blocks are provided on the inner side surfaces of the left gate plate and the right gate plate. The left lifting block is located in the left lifting groove and is drivingly matched with it. 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 drivingly matched with it. 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. A hole communicating with the outlet cavity is provided at the bottom of the valve body. The lower middle cavity can communicate with the hole through the gate plate partition cavity. A sealing plug is provided at the lower end of the central plate, and the sealing plug can move into the hole to be sealingly matched 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 diversion 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 in the upper part of the adjusting sleeve. A liquid inlet hole is arranged in the lower part of the piston plate, and the liquid inlet hole is in sealed cooperation with the pressure relief flap; A straight tooth rod is elastically liftable on the valve cover. A polygonal hole is arranged at the lower end of the straight tooth rod, and a polygonal rod is arranged in the polygonal hole. The lower end of the polygonal rod is connected to the adjusting sleeve. A worm is rotatably penetrated through the valve cover, and the worm is meshed with the straight tooth rod.

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

[0008] The upper end surface of the driving step of the valve rod is provided with a rod upper sealing surface, and a corresponding upper sealing surface for sealing cooperation is arranged on the valve cover.

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

[0010] The hole passage includes a connected lower hole and a side hole, and the lower hole is for the sealing plug to extend into.

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

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

[0013] The method for adjusting the sealing specific pressure of the flat gate valve adjusts the pressure of the medium in the lower middle cavity through the cavity pressure regulating mechanism, so as to adjust the acting force of the medium in the lower middle cavity on the left and right gate plates, and thus adjust the sealing specific pressure of the sealing pairs between the left and right gate plates and the left and right valve seats respectively.

[0014] The beneficial effects of the present invention are the improved stepped-opening double-gate flat gate valve and its sealing specific pressure adjustment method. The valve uses a cavity pressure adjustment mechanism to adjust the medium pressure in the lower middle cavity when the valve is in the closed state, adding an additional acting force to the sealing pair between the valve seat and the gate, increasing the sealing specific pressure of the sealing pair and enhancing the sealing performance. When the valve needs to be opened, the stepped-opening method is used to reduce the sealing specific pressure of the sealing pair between the valve seat and the gate, with a small opening torque, little wear on the sealing surface, and a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The following further elaborates on the specific embodiments of the present invention with reference to the accompanying drawings.

[0016] Figure 1 Schematic diagram of the closed state of the gate valve of the present invention; Figure 2 Schematic diagram of the open state of the gate valve of the present invention; Figure 3 Schematic diagram of the gate in the closed state of the gate valve of the present invention; Figure 4 Schematic diagram of the pressure relief structure of the present invention. SPECIFIC EMBODIMENTS

[0017] The drawings show the structure of the present invention, and the following further explains its relevant details with reference to the drawings. In this embodiment, refer to the attached Figures 1-4, this stepped-opening double-gate flat gate valve includes a valve body 1, a valve cover 14, a valve stem 15, a left gate 42, a right gate 56, a left valve seat 4 and a right valve seat 33. The valve body 1 includes an inlet cavity 2 and an outlet cavity 32. The left gate 42 is in sealing cooperation with the left valve seat 4, and the right gate 56 is in sealing cooperation with the right valve seat 33. The valve cover 14 covers the upper end of the valve body 1. The valve stem 15 is vertically movable through the valve cover 14, and a packing 26 is provided between the upper end of the valve stem 15 and the valve cover 14. The packing 26 is pressed by a gland 25, and the gland 25 is fixed to the top of the valve cover 14 by an adjusting fastener 24. A lifting mechanism is provided at the upper end of the valve stem 15. The lifting mechanism includes a bracket 17, a large handwheel 19, a screw sleeve 23, a plain bearing 22 and a screw 18. The screw 18 is connected to the upper end of the valve stem 15. The screw sleeve 23 is in threaded socket cooperation with the screw 18. The screw sleeve 23 is rotatably arranged in the bracket 17 through the plain bearing 22, and the upper end of the screw sleeve 23 is driven by the large handwheel 19. The upper end of the screw 18 passes through the large handwheel 19 and is provided with a protective cover 20. A longitudinally arranged observation window is provided on the protective cover 20, and an indicating block 21 is provided at the upper end of the corresponding screw 18 to display the lifting condition of the valve stem 15. A liftable piston plate 6 is provided in the middle cavity formed between the valve body 1 and the valve cover 14. A sealing ring 7 is provided on the outer periphery of the piston plate 6 and is in sealing sliding cooperation 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 passes through the piston plate 6 in a sealed manner. The piston plate 6 is driven by the valve stem 15 to lift and can be slidably arranged relative to it. Corresponding driving steps 3 and limiting blocks 5 are provided on the valve stem 15 above and below the piston plate 6. The interval between the driving step 3 and the limiting block 5 is greater than the thickness of the piston plate 6 to allow the piston plate 6 to slide relative to the valve stem 15 to achieve delayed driving. A central plate 45 is provided at the lower end of the valve stem 15. The central plate 45 is limited in the gate partition cavity between the left gate 42 and the right gate 56. Left and right disc springs 43 and 55 are respectively provided between the central plate 45 and the left gate 42 and the right gate 56. Corresponding left and right disc spring grooves 44 and 54 are provided on the central plate 45 for installing the left and right disc springs 43 and 55 respectively. Left and right lifting grooves 48 and 51 are also provided on both sides of the central plate 45. Corresponding left and right lifting blocks 67 and 68 are provided on the inner side surfaces of the left gate 42 and the right gate 56. The left and right lifting blocks 67 and 68 are at the same height. The left lifting block 67 is located in the left lifting groove 48 and is in driving cooperation with it. 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 in driving cooperation with it. 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 bottom surface 46 of the left lifting groove is higher than the bottom surface 53 of the right lifting groove, so the left gate 42 is lifted prior to the right gate 56.A hole 38 communicating with the outlet cavity 32 is provided at the bottom of the valve body 1. The lower middle cavity 31 can be communicated with the hole 38 through the gate plate partition cavity. A sealing plug 58 is provided at the lower end of the central plate 45. The sealing plug 58 can be movably inserted into the hole 38 for sealing cooperation therewith. Correspondingly, the sealing plug 58 is fixed to the switching rod 57 by a positioning screw block 59, and the switching rod 57 is fixed to the lower end of the central plate 45.;

[0018] As a further improved specific embodiment, the cavity pressure regulating mechanism includes a pressure relief structure 8 and a check structure 30 provided 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.

[0019] 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 diversion hole 62 is reserved between the pressure relief flap 61 and the inner wall of the adjusting sleeve 66. An adjusting spring 64 is arranged between the pressure relief flap 61 and the top of the adjusting sleeve 66. A pressure relief hole 65 is provided in the upper part of the adjusting sleeve 66. The liquid inlet hole 60 is provided at the lower part of the piston plate 6, and the liquid inlet hole 60 is in sealing cooperation with the pressure relief flap 61. A straight tooth rod 11 is elastically liftable on the valve cover 14. A polygonal hole 10 is provided at the lower end of the straight tooth rod 11. The polygonal rod 9 is arranged in the polygonal hole 10, and the lower end of the polygonal rod 9 is connected to the adjusting sleeve 66. A worm 13 is rotatably penetrated through the valve cover 14. The worm 13 is meshed with the straight tooth rod 11. A small handwheel 12 is connected to the outer end of the worm 13. Due to the characteristics of the worm 13 and the straight tooth rod 11, the worm 13 can drive the straight tooth rod 11 to rotate, while the lifting of the straight tooth rod 11 cannot drive the worm 13.

[0020] As a further improved specific embodiment, left guide grooves 40 and right guide grooves 41 for assisting the lifting of the left gate plate 42 and the right gate plate 56 are arranged in the valve body 1 to enable stable lifting. Lower left top blocks 39 and lower right top blocks 35 for limiting the left gate plate 42 and the right gate plate 56 are arranged at the bottom of the valve body 1 to limit the downward movement of the left gate plate 42 and the right gate plate 56 in place.

[0021] As a further improved specific embodiment, a rod upper sealing surface 29 is provided on the upper end surface of the driving step of the valve rod 15, and a corresponding cover upper sealing surface 27 for sealing cooperation therewith is provided on the valve cover 14.

[0022] As a specific implementation of further improvement, a left ferrule 47 is provided on the left lifting block 67, and a right ferrule 52 is provided on the right lifting block 68. The left ferrule 47 buffers and reduces wear between the left lifting block 67 and the left lifting groove 48, and the right ferrule 52 buffers and reduces wear between the right lifting block 68 and the right lifting groove 51.

[0023] As a specific implementation of further improvement, the duct 38 includes a connected lower duct 36 and a side duct 34. The lower duct 36 corresponds to the gate partition chamber and the sealing plug 58. The lower duct 36 allows the sealing plug 58 to extend therein. The side duct 34 communicates the lower end of the lower duct 36 with the outlet chamber 32. A maintenance port for the sealing plug 58 is provided on the valve body 1 corresponding to the lower duct 36, and a lower plug 37 is provided.

[0024] As a specific implementation of further improvement, a telescopic chamber is provided on the valve cover 14 corresponding to the straight tooth bar 11. The upper end of the straight tooth bar 11 is connected to the telescopic chamber through an upper return spring 16 to realize the elastic lifting of the straight tooth bar 11.

[0025] As a specific implementation of further improvement, the lower end surface of the valve cover 14 is in limit fit with the upper end surface of the piston plate 6, and the valve cover 14 forms the upper limit of the piston plate 6.

[0026] The opening process of the present invention: 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 rod 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 disengages from the duct 38, the lower middle chamber 31 communicates with the duct 38, and the medium in the lower middle chamber 31 sequentially enters the outlet chamber 32 through the gate partition chamber and the duct 38. The pressure of the medium in the lower middle chamber 31 decreases, and the sealing specific pressure of the sealing pair between the left valve seat 4 and the left gate 42 decreases. When the bottom surface 46 of the left lifting groove 48 contacts the left ferrule 47, the upward moving valve rod 15 and center plate 45 drive the left gate 42 to move upward. The sealing pair between the left valve seat 4 and the left gate 42 has small friction and small wear, and the opening torque is small. As the left valve seat 4 opens, the medium entering the outlet chamber 32 increases, and the sealing specific pressure of the sealing pair between the right valve seat 33 and the right gate 56 decreases. As the valve rod 15 and the center plate 45 continue to move upward, when the bottom surface of the right lifting groove 51 contacts the right ferrule 52, the upward moving valve rod 15 and center plate 45 drive the right gate 56 to move upward. The sealing pair between the right valve seat 33 and the right gate 56 has small friction and small wear, and the opening torque is also small. The right gate 56 opens, and the medium in the inlet chamber 2 enters the outlet chamber 32, and the valve opens. As the medium in the inlet cavity 2 enters the lower middle cavity 31, the piston plate 6 moves upward under the push of the medium in the lower middle cavity 31 and the drive of the valve stem 15 until the upper end face of the piston plate 6 abuts tightly against the lower end face of the valve cover 14. At this time, the valve is fully opened, and the rod sealing surface 29 in the middle of the valve stem 15 presses tightly against the cover sealing surface 27 to prevent the medium in the upper middle cavity 28 from impacting the packing 26, thereby preventing the medium in the upper middle cavity 28 from leaking out through the packing 26. During the upward movement of the piston plate 6 driving the pressure relief structure 8 and the straight tooth rod 11, since the straight teeth are provided on the outside of the straight tooth rod 11, the straight tooth rod 11 will not drive the worm 13 to rotate when it moves upward.

[0027] The closing process of the present invention: Rotate the large handwheel 19 in the reverse direction, driving the screw sleeve 23 to rotate in the reverse direction. 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 downward, and then the center plate 45, the piston plate 6 and the sealing plug 58 are driven to move downward. Since the left and right ferrules 47, 52 are respectively pressed against the bottoms 46, 53 of the left and right lifting grooves by the left and right springs 49, 50, the left and right gate plates 42, 56 are driven to move downward together. 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 respectively press tightly against the left and right valve seats 4, 33. When the lower end face of the right gate plate 56 contacts the lower right top block 35, the right gate plate 56 stops moving downward. The center plate 45 continues to move downward, and the right spring 50 continues to be compressed. The left gate plate 42 moves downward with the center plate 45. When the lower end face of the left gate plate 42 contacts the lower left top block 39, the left gate plate 42 stops moving downward. The center plate 45 continues to move downward, and the sealing plug 58 follows the center plate 45 to continue moving downward until the sealing plug 58 enters the passage 38 and forms a seal with the passage 38, isolating the lower middle cavity 31 from the passage 38, and the medium in the lower middle cavity 31 cannot continue to enter the outlet cavity 32 through the gate plate partition cavity and the passage 38; At this time, continue to rotate the large handwheel 19, driving the center plate 45, the piston plate 6 and the sealing plug 58 to move downward. During the downward movement of the piston plate 6, the volume of the lower middle cavity 31 decreases, and the medium in the lower middle cavity 31 is pressurized, so that the pressure of the medium in the lower middle cavity 31 increases. The medium in the lower middle cavity 31 acts on the left and right gate plates 42, 56, and the acting forces pressing on the left and right valve seats 4, 33 increase respectively. The sealing specific pressure of the sealing pairs between the left and right gate plates 42, 56 and the left and right valve seats 4, 33 increases, and the sealing performance between the left and right gate plates 42, 56 and the left and right valve seats 4, 33 is enhanced, further enhancing the sealing performance of the valve. During the downward movement of the piston plate 6 driving the pressure relief structure 8, since the straight teeth are provided on the outside of the straight tooth rod 11, 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.

[0028] The method for adjusting the sealing specific pressure of the flat gate valve of the present invention adjusts the medium pressure in the lower middle cavity 31 through a cavity pressure adjusting mechanism, so as to adjust the acting force of the medium in the lower middle cavity 31 on the left and right gate plates 42 and 56, thereby adjusting the sealing specific pressure of the sealing pairs between the left and right gate plates 42 and 56 and the left and right valve seats 4 and 33 respectively.

[0029] Under the assumption that there is no medium pressure in the lower middle cavity 31, the acting forces required for the sealing specific pressures of the sealing pairs between the left and right gate plates 42 and 56 and the left and right valve seats 4 and 33 are provided by the left and right disc springs respectively. However, the medium pressure in the pipeline may change. When the medium pressure in the pipeline is low, the required sealing specific pressure of the sealing pair is small, that is, the acting forces required for the left and right disc springs to act on the left and right gate plates 42 and 56 respectively are small; when the medium pressure in the pipeline is high, the required sealing specific pressure of the sealing pair is large, that is, the acting forces required for the left and right disc springs to act on the left and right gate plates 42 and 56 respectively are large; however, when the valve is installed on the pipeline, the left and right disc springs cannot be replaced, resulting in a too narrow range of valve use.

[0030] The method for adjusting the medium pressure in the lower middle cavity 31: When the left and right gate plates 42 and 56 are both in the closed state, when the large handwheel 19 is rotated to drive the valve stem 15, the piston plate 6, the center plate 45 and the sealing plug 58 to continue to move downward, observe the leakage condition of the outlet cavity 32. If there is medium leakage, reverse the small handwheel 12 to drive the worm 13 to rotate, and then drive the straight tooth rod 11 to rotate around its own axis. Due to the cooperation of the polygonal rod 9 and the polygonal hole 10, the adjusting sleeve 66 is further driven to rotate. The adjusting sleeve 66 is installed on the piston plate 6 by means of a threaded connection. When the adjusting sleeve 66 rotates and moves downward, the adjusting spring 64 is compressed, and the downward acting force of the adjusting spring 64 acting on the pressure relief flap 61 increases, and the preset opening pressure of the pressure relief structure 8 is increased.

[0031] 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 acting force of the adjusting spring 64 on the pressure relief flap 61 is balanced with the upward acting 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 acting force of the medium at the liquid inlet hole 60 on the pressure relief flap 61 is greater than the downward acting force of the adjusting spring 64 on the pressure relief flap 61, and the pressure relief flap 61 moves upward, and the pressure relief structure 8 is opened. The medium in the lower middle cavity 31 sequentially enters the upper middle cavity 28 through the liquid inlet hole 60, the diversion hole 62, the pressure relief cavity 63, and the pressure relief hole 65. When the medium pressure at the liquid inlet hole 60 is less than the preset opening pressure, the upward acting force of the medium at the liquid inlet hole 60 on the pressure relief flap 61 is less than the downward acting force of the adjusting spring 64 on the pressure relief flap 61, the pressure relief flap 61 moves downward, and the pressure relief structure 8 is closed. The medium in the lower middle cavity 31 no longer continues to enter the upper middle cavity 28, and the lower middle cavity 31 can withstand a higher medium pressure. When the piston plate 6 moves downward along with the valve stem 15, the lower middle cavity 31 continues to be compressed. When the medium pressure in the lower middle cavity 31 does not reach the preset opening pressure, it continues to rise, and the sealing specific pressure of the sealing pairs between the left and right gate plates 42 and 56 and the left and right valve seats 4 and 33 continues to increase. Continue to observe the leakage situation 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.

[0032] 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 cavity 28 is greater than the medium pressure in the lower middle cavity 31, the medium in the upper middle cavity 28 enters the lower middle cavity 31 through the check structure 30 to ensure that the medium pressure in the upper middle cavity 28 is less than or equal to the medium pressure in the lower middle cavity 31.

[0033] In summary, the above is only a preferred embodiment of the present invention and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A stepped-opening double-gate 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 is in sealing fit with the left valve seat, and the right gate is in sealing fit with the right valve seat. The valve cover is arranged on the upper end of the valve body. The valve stem is arranged through the valve cover in a liftable manner, and a lifting mechanism is arranged at the upper end of the valve stem. It is characterized in that: A liftable piston plate is arranged 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 arranged on the piston plate. The valve stem seals through the piston plate, and the piston plate is driven by the valve stem to lift and can be slidably arranged relative to it. Corresponding driving steps and limit blocks are arranged on the valve stem above and below the piston plate. A central plate is arranged at the lower end of the valve stem. The central plate is limited in the gate partition cavity between the left and right gate plates. Left and right disc springs are respectively arranged between the central plate and the left and right gate plates. Left and right lifting grooves are arranged on both sides of the central plate. Corresponding left and right lifting blocks are arranged on the inner side surfaces of the left and right gate plates. The left lifting block is arranged in the left lifting groove and is in driving cooperation with it. A left spring is arranged between the upper end of the left lifting block and the top of the left lifting groove. The right lifting block is arranged in the right lifting groove and is in driving cooperation with it. A right spring is arranged 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. A hole passage communicating with the outlet cavity is arranged at the bottom of the valve body. The lower middle cavity can communicate with the hole passage through the gate partition cavity. A sealing plug is arranged at the lower end of the central plate, and the sealing plug can move into the hole passage and be in sealing cooperation with it.

2. The staged-opening double-gate flat gate valve according to claim 1, characterized in that: 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.

3. The staged-opening double-gate flat gate valve according to claim 2, wherein: The pressure relief structure includes a liquid inlet hole, a pressure relief valve 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 valve flap is arranged at the lower port of the adjusting sleeve. A diversion hole is reserved between the pressure relief valve flap and the inner wall of the adjusting sleeve. An adjusting spring is arranged between the pressure relief valve flap and the top of the adjusting sleeve. A pressure relief hole is arranged in the upper part of the adjusting sleeve. A liquid inlet hole is arranged in the lower part of the piston plate, and the liquid inlet hole is in sealing cooperation with the pressure relief valve flap. A straight tooth rod is elastically liftable on the valve cover. A polygonal hole is arranged at the lower end of the straight tooth rod, and a polygonal rod is arranged in the polygonal hole. The lower end of the polygonal rod is connected to the adjusting sleeve. A worm is rotatably penetrated through the valve cover, and the worm is meshed with the straight tooth rod.

4. The step-by-step opening double gate flat gate valve according to claim 1, characterized in that: Left and right guiding grooves for assisting the lifting of the left and right gate plates are arranged in the valve body, and a left lower top block and a right lower top block for limiting the left and right gate plates are arranged at the bottom of the valve body.

5. The stepwise opening double gate plate 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 rod upper sealing surface, and a corresponding upper sealing surface for sealing cooperation is arranged on the valve cover.

6. The stepwise opening double-gate flat gate valve according to claim 1, wherein: A left sleeve is arranged on the left lifting block, and a right sleeve is arranged on the right lifting block.

7. The staged-opening double-gate flat gate valve according to claim 1, wherein: The hole passage includes a connected lower hole and a side hole, and the lower hole is for the sealing plug to extend into.

8. The stepped-opening double-gate flat gate valve according to claim 1, wherein: A telescopic cavity is arranged on the valve cover corresponding to the straight tooth rod, and the upper end of the straight tooth rod is connected to the telescopic cavity through an upper return spring.

9. The staged-opening double-gate flat gate valve according to claim 1, wherein: The lower end surface of the valve cover is in limit cooperation with the upper end surface of the piston plate, and the valve cover forms the upper limit of the piston plate.

10. A method for adjusting the sealing specific pressure of a hierarchical opening double-gate flat gate valve as described in claim 1, characterized in that: The medium pressure in the lower middle cavity is adjusted through the cavity pressure regulating mechanism to adjust the acting force of the medium in the lower middle cavity on the left and right gate plates, so as to adjust the sealing specific pressure of the sealing pair between the left and right gate plates and the left and right valve seats respectively.

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