Rod packing

Abstract

The rod packing will have fewer parts, be easy to assemble, and provide higher sealing performance. [Solution] The rod packing 10, which is fixed to the packing case 3 in contact with the outer circumference of the piston rod 2 of the cylinder 1 and suppresses fluid leakage from the outer circumference of the sliding piston rod 2, has a plurality of divided packing pieces 11, and is configured to be pressed radially inward from the outer circumference by a biasing member while the plurality of packing pieces 11 are fitted together. The inner circumferential surface member 20 of the packing piece 11 that abuts the outer circumference of the piston rod 2 is a separate part that can be attached to and detached from the packing piece 11 by sliding it in the circumferential direction against an inner groove 12 provided on the packing piece 11, and the inner circumferential surface member 20 is an arc-shaped member with a T-shaped or H-shaped cross-section.

Description

Technical Field

[0001] The present invention relates to a rod packing that is fixed to a packing case while being fitted around the outer periphery of a piston rod of a cylinder and suppresses leakage of fluid from the outer periphery of the sliding piston rod.

Background Art

[0002] Conventionally, a rod packing that is fixed to a packing case while being in contact with the outer periphery of a piston rod of a cylinder and suppresses leakage of fluid from the outer periphery of the sliding piston rod is known (for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Many of this type of rod packing are composed of parts with a relatively complex shape and require a certain degree of rigidity, so machining is time-consuming and the processing cost is high. And when the sliding part on the inner diameter side wears out, the whole including the outer peripheral side has to be replaced.

[0005] The present invention has been made in view of such points, and its object is to reduce the replacement cost of the rod packing by easily replacing only the inner peripheral surface side member that is relatively easy to process when the inner peripheral surface side of the rod packing wears out.

Means for Solving the Problems

[0006] In order to achieve the above object, in this invention, the replacement of the inner peripheral surface side member can be facilitated.

[0007] Specifically, in the first invention, A rod packing that is fixed to a packing case in contact with the outer circumference of the piston rod of a cylinder, and that suppresses fluid leakage from the outer circumference of the sliding piston rod, It has packing pieces that are divided into multiple sections in the circumferential direction, The packing pieces are fitted together and then pressed radially inward from the outer circumference by a biasing member. The inner circumferential surface member of the packing piece that abuts the outer circumference of the piston rod is a separate part that can be attached to and detached from the packing piece by sliding it in the circumferential direction relative to an inner groove provided in the packing piece. The inner circumferential surface member is configured as an arc-shaped member with a T-shaped or H-shaped cross-section.

[0008] According to the above configuration, the inner circumferential surface member can have a simple cross-sectional shape, and since the processing cost is relatively low, the rod packing 10 can be reused by replacing only the inner circumferential surface member. Furthermore, since the inner circumferential surface member, which is made of an arc-shaped member, can be replaced by sliding it in the circumferential direction, the replacement work is easy.

[0009] In the second invention, in the first invention, The inner circumferential surface member and the packing piece are made of the same material.

[0010] According to the above configuration, if the materials are the same, no problems will arise due to differences in the coefficient of thermal expansion between different materials.

[0011] In the third invention, in the first or second invention, The inner circumferential surface member has a T-shaped cross-section, which results in higher surface pressure with the outer circumference of the piston rod compared to a member with an H-shaped cross-section.

[0012] According to the above configuration, in the case of a T-shaped cross-section, the contact area with the outer surface of the piston rod at the tapered tip is reduced compared to a normal packing rod, resulting in higher surface pressure generated by the biasing member pressing against it. Therefore, sealing performance is improved, and the biasing member on the outer surface does not need to be tightened as much as before, making it easier to install the rod packing. [Effects of the Invention]

[0013] As explained above, according to the present invention, when the inner circumferential surface of the rod packing wears down, the cost of replacing the rod packing can be reduced by simply replacing only the inner circumferential surface member, which has a simple shape. [Brief explanation of the drawing]

[0014] [Figure 1] This is a front view showing a rod packing according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view taken along line II-II in Figure 1. [Figure 3] This is a cross-sectional view showing the packing case with the rod packing installed and its surrounding area. [Figure 4] This is a cross-sectional view showing a rod packing according to a modified embodiment of the present invention. [Modes for carrying out the invention]

[0015] Embodiments of the present invention will be described below with reference to the drawings.

[0016] As shown in Figure 1, the rod packing 10 according to this embodiment is fixed to a packing case 3 provided in, for example, the cases 5 and 6 of a compressor (not shown), in contact with the outer circumference of the piston rod 2 of the cylinder 1. The piston rod 2 reciprocates due to the rotational motion of the compressor's crank, and the piston head at its tip compresses gas in the compression chamber. This rod packing 10 is provided to prevent gas from leaking out of the compression chamber. The pressure range is not particularly limited.

[0017] A plurality of rod packings 10 may be provided in the packing case 3 in the axial direction. For example, in FIG. 3, a conventional rod packing 15 is provided adjacent to the rod packing 10 of the present embodiment in the packing case 3. For example, both are integrally rotatable with a fixing pin 16.

[0018] The material of the rod packing 10 is, for example, polytetrafluoroethylene (PTFE) filled with a filler such as carbon fiber, glass fiber, carbon, heat-resistant resin, etc. When the filler is 2% to 50%, the PTFE is 50% to 98%, and the main material is PTFE. The compounding agent and the compounding ratio are not limited to this. Also, the main material is not limited to polytetrafluoroethylene (PTFE), and for example, an injection-moldable resin such as polyether ether ketone (PEEK) or polyphenylene sulfide (PPS), which is excellent in heat resistance and slidability, may be used.

[0019] The rod packing 10 has, for example, packing pieces 11 divided into three. As shown in FIGS. 1 and 2, each packing piece 11 has an arc-shaped inner peripheral surface side member 20 that slidably contacts the outer periphery of the cylindrical piston rod 2. The inner peripheral surface side member 20 is configured to contact most of the outer periphery of the piston rod 2 in a state where the three packing pieces 11 are fitted together.

[0020] The inner peripheral surface side member 20 that contacts the outer periphery of the piston rod 2 is constituted by a separate part that can be detached from the packing piece 11 by sliding it in the circumferential direction with respect to the inner groove portion 12 provided in the packing piece 11.

[0021] The inner peripheral surface side member 20 has a retaining portion 21 on the outer peripheral side and a sliding contact portion 22 extending from the retaining portion 21 to the inner peripheral side. The width of the sliding contact portion 22 (the vertical width in FIG. 2) is thinner than the width of the packing piece 11. The inner peripheral surface side member 20 is resin-molded into an arc shape and then formed by cutting.

[0022] As shown in Figure 3, the three packing pieces 11 are fitted together and pressed radially inward by a biasing member 14 provided in the outer groove portion 13 on the outer circumference. The biasing member 14 is, for example, a circular tension coil spring when viewed from the axial direction of the piston rod 2, but other configurations such as an annular elastic member may be used as long as they can exert compressive force in the circumferential direction (and consequently the radial direction).

[0023] In this embodiment, the three packing pieces 11 have the same shape, and when the three are fitted together, they form an annular shape.

[0024] In this embodiment, since there are three packing pieces 11, the number of parts is reduced compared to designs with four or more packing pieces, assembly is easier, and the reduced number of dividing surfaces makes it easier to suppress fluid leakage on the outer circumference of the piston rod 2. Alternatively, there may be two packing pieces 11. While two pieces result in even fewer parts, this would mean two first pockets and two second pockets.

[0025] Furthermore, in this embodiment, since the three packing pieces 11 are the same shape, there is no need to change the shape of each packing piece 11, reducing the number of parts and simplifying the assembly process. While it is not necessary for all three to be the same shape, it is particularly desirable to have two or three packing pieces 11 of the same shape.

[0026] Next, the operation of the rod packing 10 according to this embodiment will be described. As described above, the rod packing 10 is fixed to the packing case 3 provided on the compressor cases 5 and 6 in a state in contact with the outer circumference of the piston rod 2.

[0027] The rod packing 10 is fixed to the packing case 3 in a state where it is appropriately tightened around the outer circumference of the piston rod 2 by assembling three packing pieces 11 in an annular shape, such that the first end of one packing piece 11 fits into the second end of the adjacent packing piece 11, and then fitting a resistive member into the outer groove 13. Although not shown in detail, the piston rod 2 reciprocates due to the rotational motion of the compressor's crank, and the piston head at its tip compresses the gas in the compression chamber. At this time, the rod packing 10 prevents gas from leaking out of the compression chamber on the outer circumference of the sliding piston rod 2. In this case, leakage from the compression chamber to the rod side can be suppressed not only when the compression chamber is under high pressure, but also under all pressure conditions during the compression process.

[0028] In this embodiment, the inner circumferential surface member 20 has a simple cross-sectional shape and is relatively inexpensive to manufacture, so the rod packing 10 can be reused by replacing only the inner circumferential surface member 20. Furthermore, since the inner circumferential surface member 20, which is made of an arc-shaped member, can be replaced by sliding it in the circumferential direction along the inner groove portion 12, the replacement work is easy.

[0029] Since the inner circumferential surface member 20 and the packing piece 11 are made of the same material, no problems arise due to differences in the coefficient of thermal expansion between dissimilar materials.

[0030] The inner circumferential surface member 20 has a T-shaped cross-section, resulting in higher surface pressure with the outer circumference of the piston rod compared to a member with an H-shaped cross-section. In other words, with a T-shaped cross-section, the contact area with the outer circumference of the piston rod at the tapered tip is reduced compared to a normal packing rod, resulting in greater surface pressure generated by the biasing member 14 pressing against it. This improves sealing performance and eliminates the need to tighten the biasing member 14 on the outer circumference as much as before, making it easier to install the rod packing 10.

[0031] According to the rod packing 10 of this embodiment, when the inner circumferential surface of the rod packing 10 wears down, the cost of replacing the rod packing 10 can be reduced by simply replacing only the inner circumferential surface member 20, which has a simple shape.

[0032] -Variations- Figure 4 shows a modified rod packing 110 according to an embodiment of the present invention, and differs from the above embodiment in that the shape of the inner circumferential surface member 120 is different. In this modified example, detailed explanations of the parts that are the same as those in Figures 1 to 3 are omitted.

[0033] In this modified example, the sliding contact portion 122 of the inner circumferential surface member 120 has the same width as the packing piece 11. Therefore, compared to the above embodiment, the contact area is larger and the surface pressure is lower, but because of its greater thickness, it has high durability against wear and tear.

[0034] In this modified rod packing 110, if wear occurs, only the inner circumferential surface member 120 needs to be replaced, thus obtaining the same effects as in the above embodiment.

[0035] The embodiments described above are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or uses. [Explanation of Symbols]

[0036] 1 cylinder 2 Piston Rods 3 Packing case 5, 6 cases 10 Rod packing 11 packing pieces 12 Inner groove 13 Outer groove 14. Biasing member 15 Conventional rod packing 16 Fixing pins 20 Inner circumferential surface side member 21 Retaining part 22 Sliding contact part 110 Rod packing 120 Inner circumferential surface side member 120 Inner circumferential surface side member 122 Sliding contact part

Claims

1. A rod packing that is fixed to a packing case in contact with the outer circumference of the piston rod of a cylinder, and that suppresses fluid leakage from the outer circumference of the sliding piston rod, It has packing pieces that are divided into multiple sections in the circumferential direction, The packing pieces are fitted together and then pressed radially inward from the outer circumference by a biasing member. The inner circumferential surface member of the packing piece that abuts the outer circumference of the piston rod is a separate part that can be attached to and detached from the packing piece by sliding it in the circumferential direction relative to an inner groove provided in the packing piece. The inner circumferential surface member is an arc-shaped member with a T-shaped cross-section, and compared to one with an H-shaped cross-section, it has a higher surface pressure with the outer circumference of the piston rod. A rod packing characterized by the following features.

2. The inner circumferential surface member and the packing piece are made of the same material. The rod packing according to feature 1.

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