Leak-proof hydraulic cylinder

Abstract

The application discloses a kind of anti-leakage hydraulic machine oil cylinder, it is related to oil cylinder technical field, including cylinder barrel and piston rod, the cylinder barrel top is separately provided with oil hole one and oil hole two being communicated with cylinder barrel interior in two ends, the first oil pipe is communicated in the inside of oil hole one, the second oil pipe is communicated in the inside of oil hole two, protection box is equipped between oil hole one and first oil pipe, between oil hole two and second oil pipe, impurity filtering assembly for filtering hydraulic oil flowing into first oil pipe and second oil pipe is equipped in the inside of protection box.The hydraulic oil flowing into or flowing out from oil hole one or oil hole two is respectively from two different paths under the restriction of impurity filtering assembly internal flow direction limiting mechanism, to avoid reverse flow hydraulic oil can drive the impurities filtered by filter screen to flow back to oil tank, help to ensure the cleanness of hydraulic oil in oil tank, to further achieve the effect of filtering and preventing leakage.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil cylinder, in particular to a kind of anti-leakage hydraulic machine oil cylinder. BACKGROUND

[0002] Oil cylinder is a kind of actuator in hydraulic cylinder hydraulic system, generally by cylinder, cylinder rod (piston rod) and sealing component are composed, cylinder inside is divided into two parts by piston, two parts are communicated with one oil hole respectively.Liquid pressure cylinder has five basic components: 1, cylinder and cylinder cover, 2, piston and piston rod, 3, sealing device, 4, buffer device, 5, exhaust device.Because the compression ratio of liquid is very small, so when one oil hole is filled with oil, the piston will be pushed to make another oil hole out of oil, the piston drives the piston rod to do the extension (retraction) movement, vice versa.

[0003] Oil cylinder is often used in hydraulic machine and other mechanical equipment that need to move up and down to process parts, it is known that the extension and retraction movement of oil cylinder relies on the in and out of hydraulic oil in cylinder, the prior art with publication number CN214304645U prevents the impurities in hydraulic oil from causing friction to the sealing element in cylinder to form leakage of hydraulic oil, which sets filter plate for filtering hydraulic oil at the pipe orifice of oil inlet pipe and oil outlet pipe.Because the flow of hydraulic oil in oil cylinder needs to be carried out on both sides of the piston, the flow will pass through oil tank, so the impurities filtered by filter plate in the technical solution will flow back to the inside of oil tank with hydraulic oil after reverse flow, thereby affecting the quality of hydraulic oil in oil tank. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides an anti-leakage hydraulic machine oil cylinder, which limits the flow of hydraulic oil from oil hole one or oil hole two into and out of the two different paths by the restriction of the internal flow direction limiting mechanism of the impurity filtering assembly, so as to avoid the impurities filtered by the filter screen from flowing back to the oil tank with the reverse flow of hydraulic oil, which helps to ensure the cleanliness of hydraulic oil in the oil tank, further achieves the effect of filtering impurities and preventing leakage, and effectively solves the problems in the background art.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: an anti-leakage hydraulic machine oil cylinder, comprising a cylinder and a piston rod, one end of the piston rod installed with a piston is inserted into the inside of the cylinder, the other end of the piston rod extends out of the outside of the cylinder, the top of both ends of the cylinder is respectively provided with oil hole one and oil hole two which are connected with the inside of the cylinder;

[0006] The inside of the oil hole one is connected with the first oil pipe, the inside of the oil hole two is connected with the second oil pipe, the protection box is arranged between the oil hole one and the first oil pipe and between the oil hole two and the second oil pipe, and the impurity filtering assembly for filtering the hydraulic oil flowing from the first oil pipe and the second oil pipe is arranged in the inside of the protection box;

[0007] The oil filter assembly includes a vertical pipe connected to the bottom end of the first oil pipe or the bottom end of the second oil pipe, one side of the bottom end of the vertical pipe is connected to a second elbow pipe, the bottom end of the second elbow pipe is connected to the inside of the oil hole one or the oil hole two, the bottom end of the vertical pipe is connected to a miscellaneous pipe, the bottom end of the miscellaneous pipe is fixed with a filter screen for filtering impurities, the filter pipe is located on one side of the second elbow pipe, the bottom end of the filter pipe is connected to the first elbow pipe, and the first elbow pipe is connected to the inside of the second elbow pipe away from one end of the filter pipe, the interior of the vertical pipe, the interior of the first elbow pipe and the interior of the second elbow are all provided with a flow limiting mechanism for limiting the flow direction of the hydraulic oil, the hydraulic oil flowing in from the first oil pipe or the second oil pipe passes through the vertical pipe, the filter pipe, the bottom ends of the first elbow pipe and the second elbow pipe in sequence and flows into the inside of the oil hole one or the oil hole two, and the hydraulic oil flowing out from the cylinder passes through the second elbow pipe, the vertical pipe, the first oil pipe or the second oil pipe in sequence and flows out.

[0008] Preferably, there are two flow direction limiting mechanisms in the second bend pipe, and the two flow direction limiting mechanisms are respectively located at the top end of the second bend pipe and above the bottom end of the first bend pipe.

[0009] Preferably, the flow direction limiting mechanism includes a fixing seat, which is fixed to the inner wall of the vertical pipe, the inner wall of the first elbow or the inner wall of the second elbow, a sealing plug is inserted into the interior of the fixing seat, a second sealing ring is embedded in the sealing plug, a plurality of springs are fixed at equal intervals on a side wall of the sealing plug close to the fixing seat, a plurality of circular holes are opened on a side of the fixing seat close to the sealing plug, the springs are arranged inside the circular holes and fixed to the fixing seat;

[0010] The sealing plug has a convex cross-section, and comprises a blocking block inserted into the interior of the fixing seat and a limiting block provided outside the fixing seat. The blocking block has a cross-sectional diameter that is the same as the inner diameter of the fixing seat, and the limiting block has a cross-sectional diameter that is larger than the inner diameter of the fixing seat.

[0011] The limit block located inside the filter tube contacts the bottom of the fixed seat, the limit block located inside the first bend pipe contacts the side wall of the fixed seat close to the second bend pipe, the limit block located at the bottom end of the second bend pipe contacts the bottom of the fixed seat, and the limit block located at the top end of the second bend pipe contacts the side wall of the fixed seat close to the vertical pipe.

[0012] Preferably, the outer wall at the top and the outer wall at the bottom of the filter pipe are both threadedly connected with threaded sleeves, and the two threaded sleeves are respectively threadedly connected to the bottom end of the vertical pipe and the top end of the first elbow.

[0013] Preferably, a first sealing ring is embedded in the middle of the inner wall of the threaded sleeve.

[0014] Preferably, the first elbow bottom end is provided with a flow rate sensor, the probe rod of the flow rate sensor extends into the first elbow for monitoring the flow rate of hydraulic oil in the first elbow, one side of the first oil pipe or the second oil pipe is provided with a buzzer, the front side of the first oil pipe is provided with an MCU control chip, and the first elbow monitors the flow rate of hydraulic oil below the set value and controls the buzzer to sound through the MCU control chip.

[0015] Preferably, the protection box comprises a box body, the buzzer is mounted on one side of the top of the box body, the MCU control chip is mounted on the front side of the box body located at the bottom of the first oil pipe, and the flow rate sensor is located outside the box body, the probe rod of the flow rate sensor penetrates through the box body and extends into the inside of the box body.

[0016] The box body covers the outside of the vertical pipe, the impurity filtering pipe, the first elbow and the second elbow.

[0017] Preferably, the protection box further comprises a through hole opened in one side of the box body, a plug-in plate is inserted into the through hole, a handle is fixed on the front side of the plug-in plate, two bolts are arranged on one side of the plug-in plate and distributed upward and downward, and the plug-in plate is fixed with the box body through the bolts.

[0018] Compared with the prior art, the present application provides a leakage-proof hydraulic machine oil cylinder, which has the following beneficial effects:

[0019] 1. By connecting an impurity filtering assembly at the top of the oil hole one and the oil hole two respectively, impurities in the hydraulic oil flowing into the cylinder barrel can be filtered out, so as to avoid the impurities from entering the cylinder barrel and causing wear of the sealing element in the cylinder barrel, and further to avoid the leakage of oil. In addition, under the restriction of the flow direction limiting mechanism in the impurity filtering assembly, the hydraulic oil flowing in and out of the oil hole one or the oil hole two flows along two different paths respectively, so as to avoid the reverse flowing hydraulic oil from flowing back to the oil tank with the impurities filtered by the filter screen, and to help ensure the cleanliness of the hydraulic oil in the oil tank, thereby further achieving the effect of filtering impurities and preventing leakage.

[0020] 2. By using two threaded sleeves, the impurity filtering pipe with the filter screen installed inside can be detachably installed between the vertical pipe and the first elbow, so that people can detach the impurity filtering pipe and then clean the impurities attached to the filter screen, thereby ensuring the filtering effect of the impurities.

[0021] 3. The flow rate sensor is used to detect the flow rate of the liquid in the first elbow. When the flow rate of the liquid in the first elbow decreases, it indicates that the mesh holes of the filter screen are blocked by impurities. The degree of impurity blockage is inversely proportional to the flow rate of the liquid in the first elbow. The slower the flow rate, the more serious the blockage of the filter screen. When the flow rate monitored by the flow rate sensor is lower than the set minimum flow rate, the MCU control chip controls the buzzer to sound, thereby reminding people to clean the impurities on the filter screen in time, and further ensuring the filtering effect of the impurities. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a front view of the present application;

[0023] Figure 2 is a top view of the present application;

[0024] Figure 3 is a sectional view of the protective box of the present application;

[0025] Figure 4 is a Figure 3 is an enlarged view of A;

[0026] Figure 5 is an exploded view of the protective box and oil hole one and oil hole two of the present application;

[0027] Figure 6 is a Figure 5 is an enlarged view of B;

[0028] Figure 7 is a structural schematic view of the impurity filtering assembly of the present application;

[0029] Figure 8 is a Figure 7 is an enlarged view of C;

[0030] Figure 9 is a structural schematic view of the flow direction limiting mechanism of the present application.

[0031] In the drawings:

[0032] 1 cylinder, 2 piston rod, 3 oil hole one, 4 oil hole two, 5 first oil pipe, 6 second oil pipe;

[0033] 7 protective box, 71 box body, 72 through hole, 73 plugboard, 74 handle, 75 bolt;

[0034] 8 impurity filtering assembly, 81 vertical pipe, 82 impurity filtering pipe, 83 first elbow, 84 second elbow, 85 threaded sleeve, 86 first sealing ring, 87 filter screen, 88 flow direction limiting mechanism, 89 flow rate sensor, 810 buzzer, 811 MCU control chip;

[0035] 881 fixing seat, 882 sealing plug, 883 second sealing ring, 884 spring, 885 circular hole. DETAILED DESCRIPTION

[0036] In order for those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below in conjunction with the drawings.

[0037] As Figures 1-3As shown, the present application provides a leakage-proof hydraulic machine oil cylinder, which comprises a cylinder barrel 1 and a piston rod 2, one end of the piston rod 2 is inserted into the inside of the cylinder barrel 1 and the other end of the piston rod 2 extends out of the cylinder barrel 1, and oil holes one 3 and two 4 are respectively arranged at the top of both ends of the cylinder barrel 1 and are connected with the inside of the cylinder barrel 1;

[0038] When the piston rod 2 is extended, the hydraulic oil is injected into the inside of the cylinder barrel 1 through the first oil pipe 5, and the hydraulic oil in the cylinder barrel 1 is discharged through the second oil pipe 6, and vice versa, when the piston rod 2 is retracted, the hydraulic oil is injected into the inside of the cylinder barrel 1 through the second oil pipe 6, and then the hydraulic oil in the cylinder barrel 1 is discharged through the first oil pipe 5, so as to complete the extension and retraction of the piston rod 2.

[0039] In order to ensure the sealing performance of the sealing element in the inside of the cylinder barrel 1 and prevent the leakage of the hydraulic oil, the inside of the oil hole one 3 is connected with the first oil pipe 5, the inside of the oil hole two 4 is connected with the second oil pipe 6, the oil hole one 3 and the first oil pipe 5 and the oil hole two 4 and the second oil pipe 6 are both provided with a protection box 7, the inside of the protection box 7 is provided with an impurity filtering assembly 8 for filtering the hydraulic oil flowing in from the first oil pipe 5 and the second oil pipe 6, and by filtering the hydraulic oil flowing into the inside of the cylinder barrel 1, the impurities in the hydraulic oil can prevent the sealing element in the inside of the cylinder barrel 1 from being abraded and causing the leakage of the hydraulic oil.

[0040] Specifically, as shown in Figure 4 、 6 and 7, the impurity filtering assembly 8 comprises a vertical pipe 81 connected with the bottom end of the first oil pipe 5 or the bottom end of the second oil pipe 6, the bottom end of the vertical pipe 81 is connected with a second elbow pipe 84, the bottom end of the second elbow pipe 84 is connected with the inside of the oil hole one 3 or the inside of the oil hole two 4, the bottom end of the vertical pipe 81 is connected with a filter pipe 82, the inside bottom end of the filter pipe 82 is fixedly provided with a filter screen 87 for filtering impurities, the filter pipe 82 is located on one side of the second elbow pipe 84, the bottom end of the filter pipe 82 is connected with a first elbow pipe 83, the one end of the first elbow pipe 83 away from the filter pipe 82 is connected with the inside of the second elbow pipe 84, the inside of the vertical pipe 81, the inside of the first elbow pipe 83 and the inside of the second elbow pipe 84 are all provided with a flow direction limiting mechanism 88 for limiting the flow direction of the hydraulic oil, and the number of the flow direction limiting mechanisms 88 in the second elbow pipe 84 is two, and the two flow direction limiting mechanisms 88 are respectively located at the top end of the second elbow pipe 84 and above the bottom end of the first elbow pipe 83.

[0041] During the extension movement of the piston rod 2, the hydraulic oil flowing into the cylinder barrel 1 from the first oil pipe 5 will sequentially pass through the vertical pipe 81, the filter pipe 82, the bottom ends of the first bend pipe 83 and the second bend pipe 84 and flow into the oil hole 3, and then flow into the cylinder barrel 1 through the oil hole 3. Then, the hydraulic oil will push the piston rod 2 to extend from the cylinder barrel 1. During the flow of the hydraulic oil, the filter 87 provided in the filter pipe 82 can filter impurities in the hydraulic oil to prevent the impurities from entering the cylinder barrel 1, thereby achieving the filtering effect.

[0042] On the contrary, during the contraction movement of the piston rod 2, the hydraulic oil in the cylinder 1 passes through the oil hole 2 4, the second bend 84, the vertical pipe 81 in sequence, and then flows out through the second oil pipe 6. In the present invention, the hydraulic oil flowing into the cylinder 1 and the hydraulic oil flowing out of the cylinder 1 pass through two different paths, so the outflowing hydraulic oil will not pass through the filter 87, nor will it drive the impurities filtered by the filter 87 to flow back into the oil tank, which helps to ensure the cleanliness of the hydraulic oil in the oil tank and further enhances the filtering effect of the present invention.

[0043] Furthermore, in the above process, the structure of the flow restriction mechanism 88 is as follows: Figure 8 and 9 As shown, the flow direction restriction mechanism 88 includes a fixed seat 881, which is fixed to the inner wall of the vertical pipe 81, the inner wall of the first elbow 83 or the inner wall of the second elbow 84. A sealing plug 882 is inserted into the interior of the fixed seat 881, and a second sealing ring 883 is embedded in the sealing plug 882. A plurality of springs 884 are fixed at equal intervals on a side wall of the sealing plug 882 close to the fixed seat 881. A plurality of circular holes 885 are opened on the side of the fixed seat 881 close to the sealing plug 882. The springs 884 are arranged inside the circular holes 885 and fixed to the fixed seat 881.

[0044] Moreover, the cross section of the sealing plug 882 is convex-shaped, and the sealing plug 882 includes a blocking block inserted into the interior of the fixed seat 881 and a limiting block provided outside the fixed seat 881. The cross-sectional diameter of the blocking block is the same as the inner diameter of the fixed seat 881, and the cross-sectional diameter of the limiting block is larger than the inner diameter of the fixed seat 881. The fixed seat 881 can be blocked by inserting the blocking block of the sealing plug 882 into the interior of the fixed seat 881. At the same time, the setting of the limiting block helps to limit the direction in which the blocking block moves out of the fixed seat 881. Figure 7As shown, the limiting block inside the filter pipe 82 is in contact with the bottom of the fixed seat 881, and the limiting block inside the first elbow pipe 83 is in contact with the sidewall of the fixed seat 881 close to the second elbow pipe 84, thus the fixed seat 881 and the sealing plug 882 installed inside the vertical pipe 81 and the first elbow pipe 83 only allow the hydraulic oil to flow from the vertical pipe 81 to the first elbow pipe 83, if the flow direction is reversed, the limiting block will block the sealing plug 882 from moving out of the fixed seat 881, similarly, the limiting block inside the bottom end of the second elbow pipe 84 is in contact with the bottom of the fixed seat 881, and the limiting block inside the top end of the second elbow pipe 84 is in contact with the sidewall of the fixed seat 881 close to the vertical pipe 81, thus the two fixed seats 881 and the sealing plug 882 installed inside the second elbow pipe 84 only allow the hydraulic oil to flow from the bottom end of the second elbow pipe 84 to the top end of the second elbow pipe 84, otherwise the limiting block will prevent the sealing plug 882 from moving out, so as to achieve the effect of limiting the flow direction of the hydraulic oil.

[0045] In addition, as shown in Figures 4-6 The protective box 7 comprises a box body 71 and a through hole 72 formed on one side of the box body 71, a plug plate 73 is inserted into the through hole 72, a handle 74 is fixed to the front side of the plug plate 73, two bolts 75 are arranged on one side of the plug plate 73, and the plug plate 73 is fixed to the box body 71 through the bolts 75, and the box body 71 covers the outside of the vertical pipe 81, the filter pipe 82, the first elbow pipe 83 and the second elbow pipe 84, and the box body 71 is arranged to protect the vertical pipe 81, the filter pipe 82, the first elbow pipe 83 and the second elbow pipe 84 from the outside;

[0046] Because the impurities filtered by the filter screen 87 will accumulate on the filter screen 87, it is necessary to clean the impurities before they completely block the filter screen 87, as shown in Figure 4 and 8 The outer wall of the top end and the outer wall of the bottom end of the filter pipe 82 are threadedly connected with threaded sleeves 85, and the two threaded sleeves 85 are threadedly connected with the bottom end of the vertical pipe 81 and the top end of the first elbow pipe 83, respectively;

[0047] People can remove the two threaded sleeves 85 from the bottom end of the vertical pipe 81 and the top end of the first elbow pipe 83 by unscrewing the bolts 75, then pulling out the plug plate 73 inserted into the through hole 72, and then rotating the two threaded sleeves 85 towards the middle, so as to disconnect the vertical pipe 81, the filter pipe 82 and the first elbow pipe 83, and make it convenient for people to disassemble the filter pipe 82, and the first sealing ring 86 is embedded in the inner wall of the threaded sleeve 85, which can also enhance the sealing performance of the connection, and after the filter pipe 82 is disassembled, it is convenient for people to pour out the impurities on the filter screen 87, achieving the effect of cleaning;

[0048] Moreover, in order to determine the clogging condition of the filter screen 87, a flow rate sensor 89 is arranged at the bottom end of the first elbow pipe 83, the probe rod of the flow rate sensor 89 extends into the first elbow pipe 83 for monitoring the flow rate of the hydraulic oil inside the first elbow pipe 83, the flow rate sensor 89 is located outside the box 71, the probe rod of the flow rate sensor 89 penetrates through the box 71 and extends into the box 71, a buzzer 810 is arranged on one side of the first oil pipe 5 or the second oil pipe 6, the buzzer 810 is installed on one side of the top of the box 71, an MCU control chip 811 is arranged on the front side of the first oil pipe 5, the MCU control chip 811 is installed on the front side of the box 71 at the bottom of the first oil pipe 5;

[0049] In the present application, when the liquid flow rate inside the first elbow pipe 83 decreases, it indicates that the mesh holes of the filter screen 87 are blocked by impurities, and the degree of impurity clogging is inversely proportional to the liquid flow rate in the first elbow pipe 83, the slower the flow rate, the more serious the clogging of the filter screen 87, when the flow rate monitored by the flow rate sensor 89 is lower than the set minimum flow rate, the MCU control chip 811 will control the buzzer 810 to sound to remind people, so that people can clean the impurities on the filter screen 87 in time, further ensuring the filtering effect of the impurities.

[0050] The basic principles and main features of the present application and the advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above examples, the above examples and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the present application.

Claims

1. A leak-proof hydraulic cylinder, comprising a cylinder barrel (1) and a piston rod (2), one end of the piston rod (2) being inserted into the inside of the cylinder barrel (1) and the other end of the piston rod (2) extending out of the cylinder barrel (1), characterized in that: The cylinder (1) is provided with oil hole one (3) and oil hole two (4) at the top of both ends respectively, which are communicated with the inside of the cylinder (1); The inside of the oil hole one (3) is communicated with the first oil pipe (5), the inside of the oil hole two (4) is communicated with the second oil pipe (6), and the oil hole one (3) and the first oil pipe (5), the oil hole two (4) and the second oil pipe (6) are all provided with protection box (7), and the inside of the protection box (7) is provided with impurity filtering assembly (8) for filtering the hydraulic oil flowing into the first oil pipe (5) and the second oil pipe (6); The impurity filtering assembly (8) comprises a vertical pipe (81) connected with the bottom end of the first oil pipe (5) or the bottom end of the second oil pipe (6), a second elbow (84) communicated with one side of the bottom end of the vertical pipe (81), the bottom end of the second elbow (84) is communicated with the inside of the oil hole one (3) or the inside of the oil hole two (4), a filter pipe (82) communicated with the bottom end of the vertical pipe (81), a filter screen (87) fixed at the bottom end of the filter pipe (82) for filtering impurities, the filter pipe (82) is located on one side of the second elbow (84), a first elbow (83) communicated with the bottom end of the filter pipe (82), the first elbow (83) is communicated with the inside of the second elbow (84) away from the filter pipe (82), and the inside of the vertical pipe (81), the inside of the first elbow (83) and the inside of the second elbow (84) are all provided with flow direction limiting mechanism (88) for limiting the flow direction of the hydraulic oil, the hydraulic oil flowing into the oil hole one (3) or the oil hole two (4) from the first oil pipe (5) or the second oil pipe (6) flows into the inside of the oil hole one (3) or the oil hole two (4) through the vertical pipe (81), the filter pipe (82), the first elbow (83) and the bottom end of the second elbow (84) in sequence, and the hydraulic oil flowing out of the inside of the cylinder (1) flows out through the second elbow (84), the vertical pipe (81), the first oil pipe (5) or the second oil pipe (6) in sequence.

2. The anti-leakage hydraulic cylinder according to claim 1, characterized in that: The number of flow direction limiting mechanisms (88) in the second elbow (84) is two, and the two flow direction limiting mechanisms (88) are located above the top end of the second elbow (84) and the bottom end of the first elbow (83) respectively.

3. A leak-proof hydraulic cylinder for a hydraulic press as claimed in claim 1, wherein: The flow direction limiting mechanism (88) comprises a fixed seat (881) fixed in the inner wall of the vertical pipe (81), the inner wall of the first elbow (83) or the inner wall of the second elbow (84), a sealing plug (882) inserted into the inside of the fixed seat (881), a second sealing ring (883) embedded on the sealing plug (882), a plurality of springs (884) fixed on the side wall of the sealing plug (882) at equal intervals, a plurality of circular holes (885) formed in the side of the fixed seat (881) close to the sealing plug (882), and the springs (884) are arranged in the circular holes (885) and fixed with the fixed seat (881). The sealing plug (882) is in the shape of a convex letter, and comprises a blocking block inserted into the fixed seat (881) and a limiting block arranged outside the fixed seat (881); the blocking block has the same cross-sectional diameter as the inner diameter of the fixed seat (881); and the limiting block has a cross-sectional diameter greater than the inner diameter of the fixed seat (881); The limiting block inside the filter pipe (82) is in contact with the bottom of the fixed seat (881); the limiting block inside the first elbow pipe (83) is in contact with the sidewall of the fixed seat (881) close to the second elbow pipe (84); the limiting block at the bottom end inside the second elbow pipe (84) is in contact with the bottom of the fixed seat (881); and the limiting block at the top end inside the second elbow pipe (84) is in contact with the sidewall of the fixed seat (881) close to the vertical pipe (81).

4. A leak-proof hydraulic cylinder for a hydraulic press as claimed in claim 1, wherein: The top end outer wall and the bottom end outer wall of the filter pipe (82) are both threadedly connected with threaded sleeves (85), and the two threaded sleeves (85) are respectively threadedly connected with the bottom end of the vertical pipe (81) and the top end of the first elbow pipe (83).

5. A leakproof hydraulic cylinder for a hydraulic press as defined in claim 4, wherein: The inner wall of the threaded sleeve (85) is inlaid with a first sealing ring (86) in the middle.

6. A leakproof hydraulic cylinder for a hydraulic press as defined in claim 1, wherein: The bottom end of the first elbow pipe (83) is provided with a flow rate sensor (89), the probe rod of the flow rate sensor (89) extends into the first elbow pipe (83), and the flow rate sensor (89) is used for monitoring the flow rate of hydraulic oil in the first elbow pipe (83); one side of the first oil pipe (5) or the second oil pipe (6) is provided with a buzzer (810); the front side of the first oil pipe (5) is provided with an MCU control chip (811); and when the flow rate of hydraulic oil monitored by the first elbow pipe (83) is lower than a set value, the buzzer (810) is controlled to emit sound through the MCU control chip (811).

7. A leakproof hydraulic cylinder for a hydraulic press as defined in claim 6, wherein: The protective box (7) comprises a box body (71), the buzzer (810) is mounted on one side of the top of the box body (71), the MCU control chip (811) is mounted on the front side of the box body (71) at the bottom of the first oil pipe (5), and the flow rate sensor (89) is located outside the box body (71), and the probe rod of the flow rate sensor (89) penetrates through the box body (71) and extends into the box body (71); The box body (71) covers the outside of the vertical pipe (81), the filter pipe (82), the first elbow pipe (83) and the second elbow pipe (84).

8. A leakproof hydraulic cylinder for a hydraulic press as defined in claim 7, wherein: The protective box (7) further comprises a through hole (72) formed in one side of the box body (71), a plug-in plate (73) is inserted into the through hole (72), a handle (74) is fixed to the front side of the plug-in plate (73), two bolts (75) are arranged on one side of the plug-in plate (73) and distributed above and below, and the plug-in plate (73) is fixed to the box body (71) through the bolts (75).

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