A combined seal piston structure for a liquid-driven piston compressor

Abstract

The present invention discloses a combined sealed piston structure of a liquid-driven piston compressor, comprising: a piston main body, and two sealing structures and a limiting mechanism are provided at the end of the piston main body. The two sealing structures are respectively a first sealing structure and a second sealing structure; wherein, the sealing structure close to the piston end is the first sealing structure; the first sealing structure first functions to seal the inner wall of the cylinder. When the first sealing structure is sealing, there is a gap between the second sealing structure and the inner wall of the cylinder under the action of the limiting mechanism; when the first sealing structure fails, the limiting mechanism releases the restriction on the second sealing structure under the push of air pressure, and expands and deforms to play a sealing role. The piston designed by the present invention activates the pantograph seal in sequence through the limiting structure during the working process, effectively prolonging the piston sealing duration and improving the safety and economy of the system operation.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and more specifically, to a combined seal piston structure for a liquid-driven piston compressor. Background Art

[0002] A liquid-driven piston compressor is a new type of compression form that uses a pantograph seal instead of the piston ring seal of a traditional reciprocating piston compressor, and is mainly used in the compression of combustible gases such as hydrogen and air. As the main sealing component on the piston, the effective operation duration of the pantograph seal determines the operation time of the liquid-driven piston compressor. However, due to factors such as high pressure, high temperature, gas source impurities, and interference fit, the sealing effect of the conventional pantograph seal is poor and the sealing duration is short. For high-pressure combustible gases such as hydrogen, due to the wide flash point range, explosion is likely to occur after leakage, leading to safety problems. In daily use, due to the frequent start-stop of the unit caused by the pantograph seal and manual maintenance and replacement, the maintenance and operation costs are increased, making the economy of the unit poor.

[0003] The traditional reciprocating piston compressor uses piston rings to seal the gap between the cylinder and the piston, restricting the amount of high-pressure gas in the cylinder from leaking into the crankcase. Considering the thermal expansion of metal and convenient installation, generally, the piston rings have cuts. When the gas is compressed, the high-pressure gas enters the piston groove through the cut, applying a circumferential expansion force to the inner wall of the piston ring to expand the piston ring, so that the piston ring is closely attached to the cylinder wall surface to achieve the sealing function. Generally, two to three piston rings are arranged on the piston, and the cuts are staggered by a certain angle to form a labyrinth seal to further reduce the leakage amount.

[0004] Since the traditional reciprocating piston compressor uses piston rings in a high-pressure and oil-containing environment, the opening part of the piston ring is filled with oil, resulting in a small leakage amount. Since hydrogen requires an oil-free working environment, the leakage amount of the piston ring during oil-free lubrication is greater than 10%, far exceeding the design allowance. Moreover, the sealing working environment of the liquid-driven piston compressor has a high pressure difference and heavy load, resulting in large wear of the sealing components. Therefore, the existing piston sealing duration is about 1000 hours, far less than the market demand of 4000 - 8000 hours. Therefore, currently, the liquid-driven piston compressor mainly uses a pantograph seal to seal the gap between the cylinder and the piston. The sealing lip of the pantograph seal is expanded by the spring tension and gas force, so that the sealing lip of the pantograph seal is closely attached to the cylinder wall surface to achieve the sealing function.

[0005] During the design process, in order to ensure that the sealing lip of the pan-seal fits tightly against the cylinder wall, the spring tension will make the sealing lip size of the pan-seal larger than the inner wall size of the cylinder, so during the assembly process, the pan-seal and the sealing surface are generally interference fit. When the spring force is large, the interference is large. If the pan-seal is placed in the cylinder for a long time, the spring will yield and deform, resulting in the spring force and gas force being unable to open the pan-seal sealing lip. In order to reduce the leakage, when multiple arrangements of piston rings are used, due to interference fit and thermal expansion, multiple pan-seal lips will be worn at the same time, so that when the pan-seal closest to the gas side fails, multiple pan-seals at the rear are also on the verge of failure. It is impossible to achieve the effect of extending the sealing time through multiple arrangements, so currently liquid-driven piston compressors generally use a single pan-seal for sealing.

[0006] Existing liquid-driven piston compressors generally use a single pan seal for sealing. After a period of use, the pan seal fails due to wear of the pan seal lip. The machine often needs to be disassembled for repair, resulting in high maintenance costs and low overall machine operating efficiency.

[0007] When multiple pan-plug seals are used for sealing, multiple pan-plug seal lips will be worn at the same time due to interference fit, which increases the cost while only slightly improving the sealing time. The problem of simultaneous wear of multiple pan-plug seals cannot be solved, resulting in a short effective operating time of the unit and low work efficiency. Summary of the invention

[0008] The object of the present invention is to provide a combined sealed piston structure for a liquid-driven piston compressor, in order to solve the technical problems in the background technology.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A combined sealed piston structure of a liquid-driven piston compressor, comprising:

[0011] A piston body, wherein the end of the piston body is provided with two sealing structures and a limiting mechanism, wherein the two sealing structures are respectively a first sealing structure and a second sealing structure; wherein the sealing structure close to the end of the piston is the first sealing structure;

[0012] The first sealing structure first seals the inner wall of the cylinder. When the first sealing structure plays a sealing role, a gap exists between the second sealing structure and the inner wall of the cylinder due to the action of the limiting mechanism. When the first sealing structure fails, the limiting mechanism releases the restriction on the second sealing structure under the push of air pressure, and expands and deforms to play a sealing role.

[0013] In some embodiments, two steps with decreasing diameters are provided on one side of the piston body facing the end, namely a first step and a second step. The second sealing structure is installed on the first step, and the first sealing structure is installed on the second step; a retaining ring for limiting is provided at the end of the piston body.

[0014] In some embodiments, the first sealing structure includes: a first lip seal. The first lip seal is sleeved on the second step.

[0015] In some embodiments, the first sealing structure further includes: a first washer. The first washer is disposed at the vertex angle of the second step and abuts against the first lip seal, for reducing the wear of the first lip seal.

[0016] In some embodiments, the second sealing structure includes a second lip seal. The second lip seal is sleeved on the first step.

[0017] In some embodiments, on the side of the second lip seal in contact with the cylinder wall, an annular limiting groove and an annular receiving groove are provided; the limiting groove is provided between the sealing lip and the receiving groove of the second lip seal; the size of the limiting groove is larger than the size of the receiving groove; the size of the limiting mechanism is larger than the size of the limiting groove, and the limiting mechanism is configured as: when the first sealing structure has not failed, when the limiting mechanism is sleeved in the limiting groove, there is a gap between the sealing lip of the second lip seal and the inner wall of the cylinder; when the first sealing structure fails, the limiting mechanism is pushed into the receiving groove by air pressure, and at the same time, the sealing lip of the second lip seal contacts the inner wall of the cylinder.

[0018] In some embodiments, the limiting mechanism includes an O-ring and a wear-resistant ring. The wear-resistant ring is of a concave open structure, and the O-ring is wrapped into a whole through the open structure.

[0019] In some embodiments, the design between the limiting groove and the receiving groove is an inverted triangular structure.

[0020] In some embodiments, the second sealing structure further includes: a second washer. The second washer is disposed on the first step and abuts against the second lip seal, for reducing the wear of the second lip seal.

[0021] In some embodiments, a third step is provided between the second step and the end of the piston. The diameter of the third step is smaller than the diameter of the second step. A dirt collecting ring support and a dirt collecting ring are installed on the third step.

[0022] The technical effects of the present invention compared with the prior art are as follows:

[0023] (1) The piston designed by the present invention activates the lip seal successively during the working process through the limiting structure, effectively prolonging the piston sealing duration and improving the safety and economy of the system operation.

[0024] (2) The wear-resistant ring and O-ring in the structure designed by the present invention adjust the contact area according to the pressure, preventing the lip seal from failing to activate and having a wide range of application scenarios. Description of the Drawings

[0025] Figure 1 Structural diagram of a liquid-driven piston compressor;

[0026] Figure 2 Structural diagram of the piston of a liquid-driven piston compressor;

[0027] Figure 3 Structural diagram of the second lip seal (not working);

[0028] Figure 4 Structural diagram of the second lip seal (working);

[0029] Figure 5 Schematic diagram of the dimensions when the second lip seal is not working;

[0030] Figure 6 Schematic diagram of the dimensions when the second lip seal is working;

[0031] Illustration: Cylinder end cover 1, pressure valve cover 2, water-cooled cylinder sleeve 3, cylinder 4, bolt 5, air valve 6, piston 7, piston rod 8, retaining ring 9, dirt trap ring support 10, dirt trap ring 11, first lip seal 12, first washer 13, second lip seal 14, second washer 15, support ring 16, piston body 17, lip seal body 18, spring 19, storage groove 20, wear-resistant ring 21, O-ring 22. Detailed Implementation Modes

[0032] To make the objectives, technical solutions and advantages of the present application clearer, the technical solutions in the preferred embodiments of the present application will be described in more detail below with reference to the drawings in the preferred embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar components or components with the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of the present application. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0033] The embodiments of the present application will be described in detail below with reference to the drawings.

[0034] In the description of the present application, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", and "coupled" should be understood in a broad sense. For example, it can be a fixed connection, or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0035] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "upper", "lower", "front", "rear", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is the orientation or positional relationship based on the drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0036] In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or display that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products, or displays.

[0037] The following will be combined with Figures 1-3 to detail a combined seal piston structure of a liquid-driven piston compressor involved in the embodiments of the present application. It should be noted that the following embodiments are only used to explain the present application and do not constitute a limitation to the present application.

[0038] Embodiment 1:

[0039] Refer to Figures 1-6 . The liquid-driven piston compressor structure composed of the combined seal piston structure of the liquid-driven piston compressor of the present invention is as shown in Figure 1 , and includes a cylinder end cover 1, a pressure valve cover 2, a water-cooled cylinder sleeve 3, a cylinder 4, a bolt 5, a gas valve 6, a piston 7, and a piston rod 8. The hydraulic mechanism pushes the piston rod 8 to move and then pushes the piston 7 to compress the gas; when the gas in the cylinder 4 reaches the exhaust pressure, the lower gas valve (exhaust valve) opens, and when the piston reaches the top dead center position, it reverses to make the piston rod and the piston move in the opposite direction, and the exhaust ends and the expansion process begins; when the pressure in the cylinder drops to the suction pressure, the upper gas valve (suction valve) opens, and the suction process begins. When the piston reaches the bottom dead center position, it reverses to make the piston rod and the piston move in the opposite direction, and the suction process ends and the compression process begins.

[0040] The present invention designs a multiple seal mechanism for the piston 7, such as Figure 2As shown in the figure, it includes a retaining ring 9, a support sleeve 10, a dirt collecting ring 11, a first lip seal 12, a first washer 13, a second lip seal 14, a second washer 15, a support ring 16 for preventing piston offset, and a piston body 17. The structure of the second lip seal 14 is as shown in Figure 3 the figure, which includes a lip seal body 18, a spring 19, a receiving groove 20, a wear-resistant ring 21, and an O-ring 22.

[0041] Two sealing structures and a limiting mechanism are provided at the end of the piston body. The two sealing structures are the first sealing structure and the second sealing structure respectively; two steps with decreasing diameters are provided on one side of the piston body facing the end, namely the first step and the second step. The second sealing structure is installed on the first step, and the first sealing structure is installed on the second step; a retaining ring for limiting is provided at the end of the piston body. A third step is provided between the second step and the piston end, and the diameter of the third step is smaller than that of the second step. A dirt collecting ring support and a dirt collecting ring are installed on the third step. The dirt collecting ring is used to collect impurities in the cylinder.

[0042] Among them, the sealing structure closer to the piston end is the first sealing structure; the first sealing structure first seals the inner wall of the cylinder. When the first sealing structure is sealing, there is a gap between the second sealing structure and the inner wall of the cylinder under the action of the limiting mechanism; when the first sealing structure fails, the limiting mechanism releases the restriction on the second sealing structure under the push of air pressure, and expands and deforms to play a sealing role.

[0043] In some embodiments, the first sealing structure includes: a first lip seal, and the first lip seal is sleeved on the second step. The first sealing structure further includes: a first washer, and the first washer is arranged at the vertex of the second step and abuts against the first lip seal to reduce wear of the first lip seal.

[0044] In some embodiments, the second sealing structure includes a second lip seal and a second washer. The second washer is arranged on the first step and abuts against the second lip seal to reduce wear of the second lip seal.

[0045] The second PTFE seal ring is arranged on the first step. On the side of the second PTFE seal ring contacting the cylinder wall, there are an annular limiting groove and an annular receiving groove. The limiting groove is arranged between the sealing lip and the receiving groove of the second PTFE seal ring; the size of the limiting groove is larger than that of the receiving groove; the size of the limiting mechanism is larger than that of the limiting groove, and the limiting mechanism is configured such that: when the first sealing structure has not failed, when the limiting mechanism is sleeved in the limiting groove, there is a gap between the sealing lip of the second PTFE seal ring and the inner wall of the cylinder; when the first sealing structure fails, the limiting mechanism is pushed into the receiving groove by air pressure, and at the same time, the sealing lip of the second PTFE seal ring contacts the inner wall of the cylinder.

[0046] When the first PTFE seal ring has not failed and the second PTFE seal ring is not working, as Figure 3 shown. Under the action of the elastic force of the inner spring of the first PTFE seal ring and the gas pressure, the outer diameter of the first PTFE seal ring expands to closely fit with the inner wall of the cylinder, so that the cylinder is kept in a sealed state. In the initial state, the wear-resistant ring 21 and the O-ring 22 of the second PTFE seal ring are in the limiting groove. The compressive strength of the O-ring is sufficient to limit the sealing lip of the PTFE seal ring within the inner diameter of the cylinder, and the material used is nitrile. The maximum outer diameter at the sealing lip of the second PTFE seal ring is limited so that it is always smaller than the inner diameter of the cylinder. The wear-resistant ring outside the O-ring is designed with an open structure to prevent the O-ring from expanding due to heat during movement and losing its limiting function due to friction and deformation with the cylinder; when the first PTFE seal ring fails and high-pressure gas leaks to the second PTFE seal ring, as Figure 4 shown. The gas pressure and frictional force of the high-pressure gas push the O-ring 22 and the wear-resistant ring 21 into the receiving groove 20, and the second PTFE seal ring is activated. Under the action of the gas force and the spring force, the outer wall surface of the sealing lip closely fits with the inner wall of the cylinder to achieve a sealing effect.

[0047] The area between the limiting groove and the receiving groove is designed as an inverted triangular structure, which is convenient for the gas to push the wear-resistant ring 21 and the O-ring 22 into the receiving groove 20, and at the same time prevents the wear-resistant ring 21 and the O-ring 22 from returning to the initial position through frictional force; when the PTFE seal ring is not under external force, the elastic force of the inner spring of the PTFE seal ring should be sufficient to expand the outer diameter of the PTFE seal ring to closely fit with the inner wall of the cylinder, so that the cylinder is kept in a sealed state; as the main friction part, the wear-resistant ring is made of PTFE material. The wear-resistant ring is designed in a concave structure to increase the contact area with the O-ring.

[0048] According to the different working pressures of the used environment, the contact surface between the wear-resistant ring and the O-ring will be adjusted accordingly. The higher the pressure, the larger the contact area. To prevent the gas force from being too small to push the wear-resistant ring and the O-ring, resulting in the failure of the activation of the second lip seal, or the frictional force of the wear-resistant ring being too large, pushing the wear-resistant ring and the O-ring into the receiving groove, activating the second lip seal in advance, and failing to achieve the effect of sequential activation and extended sealing duration; considering that during the operation of the unit, the gas will be heated to 200 °C, and the dirt collection ring is made of CFRP material, which has the advantages of low density, small coefficient of thermal expansion, and good heat ablation resistance.

[0049] The following is an example to illustrate the process of the limiting mechanism being blown from the limiting groove to the receiving groove;

[0050] During the design, when in the non-working state, the radius dimension of the groove where the O-ring is located is 51 mm, the radius dimension of the O-ring is 50 * 56 mm, the radius dimension of the wear-resistant ring is 56 * 59.5 mm, the radius dimension of the receiving groove is 50.1 mm, and the cylinder radius is 60 mm.

[0051] Regarding the O-ring and the wear-resistant ring as a whole (limiting mechanism), at this time, the size of the limiting mechanism is 50 * 59.5 mm. Since the O-ring is a plastic structure, a deformation amount is allowed. At the same time, the wear-resistant ring is an open structure, and a deformation amount is also allowed.

[0052] When the lip seal is in the non-working state, such as Figure 5 , the size of the initial position groove is larger than the inner diameter of the limiting mechanism (51 - 50 = 1 mm), resulting in the limiting mechanism being propped up by 1 mm. However, the cylinder radius is 60 mm (59.5 + 1 = 60.5 > 60), so at this time, the limiting mechanism is compressed by 0.5 mm by itself and expands outward by 0.5 mm to closely fit with the cylinder wall surface.

[0053] When the lip seal is in the working state, such as Figure 6 , the size of the receiving groove is larger than the inner diameter of the limiting mechanism (50.1 - 50 = 0.1 mm), resulting in the limiting mechanism being propped up by 0.1 mm. However, the inner diameter of the cylinder is 60 mm (59.5 + 0.1 = 59.6 > 60), so the limiting mechanism cannot fit with the cylinder wall surface. At the same time, due to the interference fit, the limiting mechanism is fixed in the receiving groove and will not move.

[0054] The above are only the preferred embodiments of the present invention and are used to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A combined sealed piston structure for a liquid-driven piston compressor, characterized in that: include: A piston body, wherein the end of the piston body is provided with two sealing structures and a limiting mechanism, wherein the two sealing structures are respectively a first sealing structure and a second sealing structure; wherein the sealing structure close to the end of the piston is the first sealing structure; The first sealing structure first seals the inner wall of the cylinder. When the first sealing structure is sealing, a gap exists between the second sealing structure and the inner wall of the cylinder under the action of the limiting mechanism. When the first sealing structure fails, the limiting mechanism releases the restriction on the second sealing structure under the push of air pressure, and expands and deforms to seal. The piston body is provided with two steps with smaller diameters on one side facing the end, which are the first step and the second step. The second sealing structure is installed on the first step, and the first sealing structure is installed on the second step. The end of the piston body is provided with a retaining ring for limiting the position. The first sealing structure comprises: a first flood seal, wherein the first flood seal sleeve is arranged on the second step; The first sealing structure further includes: a first gasket, which is arranged at the top corner of the second step and abuts against the first flood seal to reduce wear of the first flood seal; The second sealing structure comprises a second flood seal, wherein the second flood seal sleeve is arranged on the first step; The second pan-seal is provided with an annular limiting groove and an annular receiving groove on the side in contact with the cylinder wall, the limiting groove is arranged between the sealing lip of the second pan-seal and the receiving groove; the size of the limiting groove is larger than the size of the receiving groove; the size of the limiting mechanism is larger than the size of the limiting groove, and the limiting mechanism is configured as follows: when the first sealing structure has not failed, when the limiting mechanism is sleeved in the limiting groove, there is a gap between the sealing lip of the second pan-seal and the inner wall of the cylinder; when the first sealing structure fails, the limiting mechanism is pushed into the receiving groove by air pressure, and at the same time the sealing lip of the second pan-seal contacts the inner wall of the cylinder.

2. A combined sealed piston structure for a liquid-driven piston compressor according to claim 1, characterized in that: The limiting mechanism comprises an O-ring and a wear-resistant ring. The wear-resistant ring is a concave opening structure, and the O-ring is wrapped into a whole through the opening structure.

3. The combined sealed piston structure of a liquid-driven piston compressor according to claim 1, characterized in that: The space between the limiting groove and the receiving groove is designed to be an inverted triangle structure.

4. A combined sealed piston structure for a liquid-driven piston compressor according to claim 1, characterized in that: The second sealing structure further includes: a second gasket, which is arranged on the first step and abuts against the second pan-plug seal to reduce wear of the second pan-plug seal.

5. The combined sealed piston structure of a liquid-driven piston compressor according to claim 1, characterized in that: A third step is provided between the second step and the piston end, the diameter of the third step is smaller than the diameter of the second step, and a dirt containing ring support and a dirt containing ring are installed on the third step.

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