Shaft seal

Abstract

To provide a shaft seal capable of keeping a sufficiently high seal pressure of a packing at a low temperature, without excessively increasing the same at a normal temperature.SOLUTION: A shaft seal for sealing a clearance between a movable shaft of fluid equipment and a staffing box includes a resin packing and a support body. The packing fills a clearance between the movable shaft and the staffing box by axial pressure from a packing pressor. The support body is an annular structure surrounding the movable shaft, of which one side in an axial direction is kept into contact with one end portion in an axial direction of the packing and the other side is kept into contact with the staffing box or the packing pressor. The support body includes a fastening region at least partially in the axial direction. An outer peripheral side of the fastening region has a thermal shrinkage higher than that of an inner peripheral side, and the outer peripheral side fastens the inner peripheral side in temperature drop. The support body is constituted so that a force for fastening the inner peripheral side by the outer peripheral side of the fastening region is transferred from the fastening region to the packing as the pressure in the axial direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a shaft seal, and more particularly to a shaft seal including a resin packing. [Background technology]

[0002] A "shaft seal" is a general term for components that seal the gap between the casing opening and the movable shaft of a fluid equipment, i.e., components that prevent fluid leakage through the gap or the intrusion of foreign objects into the gap. Some shaft seals, in particular, include packing packed into a stuffing box (see, for example, Patent Documents 1-6). A "stuffing box" is a tubular member fitted inside the casing opening, surrounding the movable shaft and forming an annular space, i.e., a packing chamber, between its inner circumferential surface and the outer circumferential surface of the movable shaft. A "packing" is a flexible member, either string-like or annular, and multiple packings are generally packed into the packing chamber. Within the packing chamber, multiple packings are arranged side by side along the movable shaft, either wrapped around the movable shaft if they are string-like or with the movable shaft threaded through its inner circumferential surface if they are annular, forming a cylindrical structure surrounding the movable shaft. When compressed axially by an annular member called a "packing gland," this cylindrical structure expands radially, adhering tightly to the inner circumferential surface of the stuffing box and the outer circumferential surface of the movable shaft. As a result, the packing chamber is closed, and the gap between the opening of the casing and the movable shaft is sealed.

[0003] The pressure of the packing against the inner circumferential surface of the stuffing box and the outer circumferential surface of the movable shaft, i.e., the sealing pressure, is the result of increased radial stress caused by axial compression of the packing. Therefore, when stress relaxation occurs in the packing—a phenomenon in which stress decreases due to creep deformation, wear, temperature drop, etc.—the sealing pressure decreases. To prevent an increase in fluid leakage due to this stress relaxation, work is required to increase the pressure of the packing gland against the packing, i.e., retightening. One known technique for reducing the frequency of retightening and easing the maintenance burden related to shaft seals is to install a spring in the stuffing box or packing gland that applies axial pressure to the packing (see, for example, Patent Documents 3-6). When the packing reduces its axial stress due to stress relaxation, the spring pressure further compresses it in the axial direction. This increases the radial stress of the packing, offsetting the decrease due to stress relaxation, making it less likely to reduce the sealing pressure. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Utility Model Application Publication No. 02-084062 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-020711 [Patent Document 3] Japanese Patent Application Publication No. 11-344123 [Patent Document 4] Japanese Patent Application Laid-Open No. 2005-220832 [Patent Document 5] Japanese Patent Application Laid-Open No. 2009-215905 [Patent Document 6] Patent No. 5820793 Summary of the Invention [Problem to be solved by the invention]

[0005] Resins are often chosen as packing materials. Fluoropolymers, such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and polyvinylidene fluoride (PVDF), are particularly popular due to their high heat resistance, excellent chemical stability against fluids, and low coefficient of friction with moving shafts. However, compared to the metals typically used for moving shafts and stuffing boxes, resins, especially fluoropolymers, have a thermal shrinkage rate that is about 10 times higher. This means that using resin packing for shaft seals poses the following problems: The term "thermal shrinkage rate" refers to the rate at which an object thermally shrinks, i.e., the rate at which an object's volume or length decreases as its temperature drops. It is actually equal to the object's thermal expansion coefficient.

[0006] When fluid equipment handles low-temperature fluids (below -100°C), such as liquefied natural gas (LNG, boiling point -160°C), liquid nitrogen (-196°C), liquid hydrogen (-253°C), or liquid helium (-269°C), the fluid cools not only the moving shaft but also the shaft seal to low temperatures. Compared to metal moving shafts and stuffing boxes, resin packings generally have a higher thermal shrinkage rate. Therefore, when the temperature drops from room temperature (above -10°C or below -10°C) to low temperatures (hereinafter referred to as "low-temperature"), the packing's radial width shrinks more than the inner radial dimension of the packing chamber. As a result, the seal pressure decreases, especially around the outer periphery of the packing. Furthermore, because the difference in thermal shrinkage rate between the packing chamber and the packing is large, the seal pressure decrease with low temperature is significantly greater than the decrease due to stress relaxation at room temperature, such as creep deformation or wear.

[0007] Even when packing is pressurized with a spring, as in the shaft seals disclosed in Patent Documents 3-6, the spring pressure is only sufficient to prevent a decrease in sealing pressure due to stress relaxation of the packing at room temperature, but is insufficient to prevent a decrease in sealing pressure due to low temperatures. However, pressurizing the packing with a stronger spring is difficult because it requires a stronger or larger stuffing box or gland structure. Even if a sufficiently strong spring is attached to the stuffing box, the spring pressure exceeds the required level at room temperature, causing an excessive increase in the packing's sealing pressure. This results in excessively rapid wear of the packing and excessively high sliding resistance of the packing against the movable shaft. To avoid these problems, a method is needed to reduce the spring pressure at room temperature compared to low temperatures. However, such a method is difficult.

[0008] The object of the present invention is to solve the above problems, and in particular to provide a shaft seal that can maintain a sufficiently high sealing pressure of the packing at low temperatures without excessively increasing the sealing pressure at room temperature. [Means for solving the problem]

[0009] A shaft seal according to one aspect of the present invention is for sealing the gap between a movable shaft and a stuffing box of a fluid device, and includes a resin packing and a support. The packing is packed into the gap between the movable shaft and the stuffing box by axial pressure from the packing gland. The support is an annular structure surrounding the movable shaft, with one axial side in contact with one axial end of the packing and the other side in contact with the stuffing box or the packing gland. The support includes a clamping region in at least a portion of the axial direction. The outer periphery of the clamping region has a higher thermal shrinkage rate than the inner periphery, and as the temperature drops, the outer periphery clamps the inner periphery. The support is configured so that this clamping force is transmitted from the clamping region to the packing as axial pressure.

[0010] The support may have a variety of specific configurations. For example, the support may include a clamping ring and a pressing ring. The clamping ring is an annular member that surrounds the movable shaft and includes a tapered inner peripheral surface on the side closer to the packing in the axial direction. The tapered inner peripheral surface is inclined so that the diameter narrows from the end to the center in the axial direction. The pressing ring is an annular member that surrounds the movable shaft and has a lower thermal shrinkage rate than the clamping ring and includes a tapered outer peripheral surface on the side farther from the packing in the axial direction. The tapered outer peripheral surface is inclined so that the diameter narrows from the center to the end in the axial direction. In the clamping region, the tapered inner peripheral surface of the clamping ring contacts the tapered outer peripheral surface of the pressing ring.

[0011] In addition to the above, the support may have a pressing ring and a stationary ring. The pressing ring is an annular member that surrounds the movable shaft and includes a tapered inner peripheral surface on the side farther from the packing in the axial direction. The tapered inner peripheral surface is inclined so that the diameter increases from the center to the end in the axial direction. The stationary ring is an annular member that surrounds the movable shaft and has a lower thermal shrinkage rate than the pressing ring and includes a tapered outer peripheral surface on the side closer to the packing in the axial direction. The tapered outer peripheral surface is inclined so that the diameter increases from the end to the center in the axial direction. In the clamping region, the tapered inner peripheral surface of the pressing ring contacts the tapered outer peripheral surface of the stationary ring.

[0012] The packing may be a V-packing. Furthermore, the support may have a male adapter that contacts one end of the packing in the axial direction. "V-packing" refers to a lip packing with a V-shaped cross section, i.e., a molded packing (a packing in which the material is molded in a mold) that includes a protruding portion called a "lip." In a V-packing, the two upper ends of the V-shape formed by the cross section correspond to the lips. "Male adapter" refers to a member that supports the V-packing from its lip side. [Effects of the Invention]

[0013] In the shaft seal of the present invention, the support is sandwiched axially between the gland and the packing, or between the packing and the stuffing box. At room temperature, the support transmits axial pressure from the gland or stuffing box, which is generated by the connection between the gland and the stuffing box, to the packing. On the other hand, at low temperatures, the support not only transmits axial pressure from the gland to the packing, but also generates axial pressure on the packing itself in the following manner.

[0014] When a low-temperature fluid flows through the casing of a fluid equipment, not only the packing but also the support body cools. As a result, the support body transmits the force of the outer periphery of the clamping area clamping against the inner periphery to the packing as axial pressure. There are various specific configurations of the support body, including, for example, the combination of (1) a clamping ring and a pressing ring, and (2) a pressing ring and a stationary ring, as described above.

[0015] (1) The pressure ring is sandwiched between the packing and the clamping ring in the axial direction, with its tapered outer surface in contact with the tapered inner surface of the clamping ring. As the pressure ring is clamped by the clamping ring due to the temperature drop, the tapered outer surface is subjected to pressure from the tapered inner surface. The tapered outer surface and the tapered inner surface are inclined so that their diameters increase as they approach the packing, so the pressure the tapered outer surface receives from the tapered inner surface is inclined relative to the radial direction. Therefore, axial stress is generated within the pressure ring and transmitted from the pressure ring to the packing as axial pressure. Meanwhile, the reaction force received by the tapered inner surface from the tapered outer surface is also inclined relative to the radial direction, so axial stress is also generated within the clamping ring and transmitted from the clamping ring to the stuffing box or packing gland as axial pressure. However, because both the stuffing box and the packing gland have sufficient rigidity, they are not substantially deformed or displaced by the axial pressure from the clamping ring. As a result, the clamping ring cannot be substantially displaced in the axial direction, and the pressure of the pressing ring against the packing is high.

[0016] (2) The pressure ring is sandwiched between the packing and the stationary ring in the axial direction, with its tapered inner peripheral surface in contact with the tapered outer peripheral surface of the stationary ring. As the pressure ring tightens the stationary ring due to the temperature drop, the tapered inner peripheral surface applies pressure to the tapered outer peripheral surface. The tapered inner peripheral surface and the tapered outer peripheral surface are inclined so that the diameter narrows as they approach the packing, so the pressure applied by the tapered inner peripheral surface to the tapered outer peripheral surface is inclined relative to the radial direction. Therefore, the reaction force to this pressure is also inclined relative to the radial direction, so axial stress is generated within the pressure ring and transmitted from the pressure ring to the packing as axial pressure. Meanwhile, the pressure applied by the tapered inner peripheral surface to the tapered outer peripheral surface also generates axial stress within the stationary ring, which is transmitted from the stationary ring to the stuffing box or packing gland as axial pressure. However, because both the stuffing box and the packing gland are sufficiently rigid, they are not substantially deformed or displaced by the axial pressure from the stationary ring. As a result, the pressure of the pressure ring against the packing is high because the stationary ring cannot be substantially displaced in the axial direction.

[0017] Thus, at low temperatures, the packing is subjected not only to axial pressure due to the bond between the packing gland and the stuffing box, but also to axial pressure due to thermal contraction of the clamping area of the support. Therefore, the packing is further compressed in the axial direction, increasing radial stress. This increase offsets the decrease in radial stress due to the packing's low temperature, making it possible to maintain a sufficiently high sealing pressure of the packing even at low temperatures. Thus, the shaft seal according to the present invention can maintain a sufficiently high sealing pressure of the packing at low temperatures without excessively increasing it at room temperature.

[0018] When the packing is a V-packing and the support includes a male adapter, the support is located on the lip side of the V-packing. Therefore, the axial pressure from the pressure ring, which increases with the temperature, not only compresses the V-packing in the axial direction, but also opens the lip of the V-packing further, pressing it more firmly against the stuffing box and the movable shaft. As a result, the packing's sealing ability at low temperatures is further improved. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1(a) is a cross-sectional view of a shaft seal according to a first embodiment of the present invention, and FIG. 1(b) is a partially enlarged view of the packing and its vicinity shown in FIG. [Figure 2] FIG. 2 is an exploded view of the shaft seal shown in FIG. [Figure 3] FIG. 1(a) is a schematic diagram showing the force transmitted from the clamping ring to the pressing ring and then to the packing as the temperature drops, and FIG. 1(b) is a schematic diagram showing the deformation of the packing and the displacement of the pressing ring as the clamping ring thermally shrinks. [Figure 4] FIG. 3 is a cross-sectional view of a modified example of the shaft seal according to the first embodiment of the present invention. [Figure 5] FIG. 10(a) is a cross-sectional view of a shaft seal according to a second embodiment of the present invention, and FIG. 10(b) is a partially enlarged view of the packing and its vicinity shown in FIG. [Figure 6] FIG. 6 is an exploded view of the support shown in FIG. [Figure 7] 1A is a schematic diagram showing the force transmitted from the pressing ring to the stationary ring and packing as the temperature drops, and FIG. 1B is a schematic diagram showing the displacement of the pressing ring and the deformation of the packing as the pressing ring thermally shrinks. DETAILED DESCRIPTION OF THE INVENTION

[0020] A shaft seal according to an embodiment of the present invention is used, for example, to seal the gap between the opening of a valve casing and the stem. The "casing," also known as the "valve box," is a housing that houses a flow path inside. The "stem," also known as the "valve rod," is a rod-shaped member that transmits power to the valve element of the valve by rotating around its central axis or by reciprocating along the central axis. Since the power is transmitted to the flow path inside the casing, an opening is essential in the casing to allow the stem to pass through. The shaft seal according to an embodiment of the present invention reduces the amount of fluid leaking from this opening. First Embodiment

[0021] FIG. 1(a) is a cross-sectional view of a shaft seal 100 according to a first embodiment of the present invention. The shaft seal 100 seals the gap between a valve stem 510 and an opening 551 in a casing 550. The cross section shown in FIG. 1(a) includes the central axis of the stem 510. In FIG. 1(a), the central axis of the stem 510 is parallel to the left-right direction, with a flow path 540 inside the casing 550 located on the right side and an external space 560 of the casing 550 extending to the left side, generally communicating with the outside air. Hereinafter, the right side of any portion shown in FIG. 1(a) (i.e., the side closer to the flow path 540) will be referred to as the "fluid side," and the left side (i.e., the side farther from the flow path 540) will be referred to as the "atmosphere side."

[0022] A stuffing box 520 is fitted inside the opening 551 of the casing 550. The stuffing box 520 is a cylindrical member made of metal such as brass, bronze, steel, or cast iron, and coaxially surrounds the stem 510. A fluid-side end 521 (the right end in FIG. 1(a)) of the stuffing box 520 faces the flow path 540 inside the casing 550, and an air-side end 522 (the left end in FIG. 1(a)) protrudes outside the casing 550. An inner circumferential surface 523 of the stuffing box 520 forms a cylindrical packing chamber between itself and the outer circumferential surface 511 of the stem 510. An annular rib 524 protrudes from the fluid-side end 521 of the stuffing box 520 toward the outer circumferential surface 511 of the stem 510, separating the flow path 540 from the packing chamber.

[0023] Inside the atmosphere-side end 522 (left end in FIG. 1) of the stuffing box 520, a packing gland 530 closes the opening on the atmosphere side (left side in FIG. 1) of the packing chamber at its fluid-side end 531 (right end in FIG. 1). The packing gland 530 is a circular member made of a metal such as brass, bronze, steel, or cast iron, and coaxially surrounds the stem 510. An annular flange 533 projects outward from the atmosphere-side end 532 (left end in FIG. 1) of the packing gland 530. A plurality of bolts 534 penetrate the flange 533 parallel to the stem 510 (left-right direction in FIG. 1), securing the flange 533 to the atmosphere-side end 522 of the stuffing box 520. [Shaft seal structure]

[0024] The shaft seal 100 is a group of parts for sealing a packing chamber, and includes a packing 120, a female adapter 140, and supports 150 and 160. -rubber seal-

[0025] FIG. 1(b) is a partially enlarged view of the packing 120 shown in FIG. 1(a) and its vicinity (the area surrounded by the dashed line in FIG. 1(a)), and FIG. 2 is an exploded view of the shaft seal 100. The packing 120 is a V-packing, and is composed of, for example, four V-rings 121. "V-ring" refers to a V-packing that forms a single ring shape. In the following, to avoid confusion with "V-rings," "V-packing" will only be used as the overall name for the V-rings packed into the packing chamber.

[0026] Each V-ring 121 is an annular molded packing made of fluororesin such as PTFE, and its cross section (a cross section taken along a plane including the central axis of the annular shape) is V-shaped, with the axial direction of the V-ring 121 as the up-down direction. The two upper ends of this V-shape, i.e., lips 122 and 123, extend to one side of the V-ring 121 in the axial direction (the right side in FIG. 1) and are connected circumferentially around the V-ring 121 to form two concentric rings. The inner lip 122 has a minimum inner diameter that is equal to or smaller than the diameter of the stem 510, and the outer lip 123 has a maximum outer diameter that is equal to or larger than the diameter of the inner circumferential surface 523 of the stuffing box 520. Due to the flexibility of their materials, the lips 122 and 123 can be bent to increase or decrease the opening of the V-shape (the vertical distance in FIG. 1). The lower end 124 of the V-shape (hereinafter referred to as the "heel") protrudes axially away from the lips 122 and 123 (to the left in FIG. 1 ) of the V ring 121 and extends circumferentially around the V ring 121 to form a single ring. The cross section of the heel 124 is tapered in the axial direction of the V ring 121, with the inner diameter widening and the outer diameter narrowing toward the tip. The four V rings 121 are pressed into the packing chamber with the lips 122 and 123 facing the fluid side (to the right in FIG. 1 ) and the stem 510 coaxially passing through the inside, and are arranged side by side along the stem 510. At this time, the heel 124 of another V ring 121 adjacent to the V ring 121 on the fluid side (to the right in FIG. 1 ) is fitted between the lips 122 and 123 of each V ring 121. This integrates the four V rings 121 into a single cylindrical structure, i.e., the V packing 120. -Female adapter-

[0027] Female adapter 140 is a circular member made of metal such as bronze or aluminum bronze, and is adjacent to the atmosphere side (left side in FIG. 1 ) of V-packing 120, coaxially surrounding stem 510. The inner diameter of female adapter 140 is slightly larger than the diameter of stem 510, and the outer diameter is slightly smaller than the diameter of inner circumferential surface 523 of stuffing box 520. This ensures that the sliding resistance of female adapter 140 relative to stem 510 is sufficiently low, and that female adapter 140 can slide along stem 510.

[0028] The term "female adapter" originally refers to a component that supports the V-packing from its heel side. The female adapter 140 also supports the V-packing 120 from the heel 124 side of each V-ring 121, i.e., the atmosphere side (left side in FIG. 1). In fact, the annular surface 141 on the atmosphere side (left side in FIG. 1) of the female adapter 140 contacts the fluid-side end (right end in FIG. 1) 531 of the packing gland 530. Meanwhile, the annular surface on the fluid side (right side in FIG. 1) of the female adapter 140, i.e., the side that contacts the V-packing 120, has an annular recess 142 extending in the circumferential direction. The heel 124 of the V-ring 121 located closest to the atmosphere (left side in FIG. 1) is fitted into the recess 142. In particular, the entire outer surface of the heel 124 is in close contact with the entire inner surface of the recess 142. Since the female adapter 140 has higher rigidity than the V-ring 121, its close contact with the heel 124 transmits the pressure from the packing gland 530 evenly to the entire circumference of the heel 124, and suppresses excessive deformation and protrusion of the heel 124 caused by friction with the stem 510 and fluid pressure. -Support-

[0029] FIG. 2 includes an exploded view of the supports 150 and 160. The supports are composed of a pressure ring 150 and a clamping ring 160. The pressure ring 150 is a circular member made of a metal such as bronze or aluminum bronze, and is adjacent to the fluid side (right side in FIG. 1) of the V-packing 120, coaxially surrounding the stem 510. The pressure ring 150 has an inner diameter slightly larger than the diameter of the stem 510 and an outer diameter slightly smaller than the diameter of the inner circumferential surface 523 of the stuffing box 520, so that the sliding resistance against the stem 510 is sufficiently low and the clamping ring 160 can slide along the stem 510. The clamping ring 160 is a circular member made of a fluororesin such as PTFE, and is adjacent to the fluid side (right side in FIG. 1) of the pressure ring 150, and coaxially surrounding the stem 510. The tightening ring 160 has an inner diameter larger than the diameter of the stem 510, so it does not provide sliding resistance to the stem 510, while its outer diameter is equal to or larger than the diameter of the inner peripheral surface 523 of the stuffing box 520, so it is fixed to the inner peripheral surface 523 by press-fitting.

[0030] The pressure ring 150 functions as a male adapter for the V-packing 120. A series of annular projections 151 protrude from the air side (left side in FIG. 1 ) of the pressure ring 150, i.e., the annular surface on the side that contacts the V-packing 120. The projections 151 are fitted between the lips 122 and 123 of the V-ring 121 located closest to the fluid (right side in FIG. 1 ). The pressure ring 150 has a tapered outer peripheral surface 152 on its fluid side (right side in FIG. 1 ). The tapered outer peripheral surface 152 is inclined so that its diameter narrows from the center of the pressure ring 150 axially toward the fluid-side end (right end in FIG. 1 ). The tapered outer peripheral surface 152 contacts the clamping ring 160 (see below for details). This allows the pressure ring 150 to be supported by the inner peripheral surface 523 and ribs 524 of the stuffing box 520 via the clamping ring 160. Since the pressure ring 150 is more rigid than the V-ring 121, it transmits the axial pressure from the ribs 524 of the stuffing box 520 that accompanies the connection between the stuffing box 520 and the packing gland 530 evenly to the entire circumference of the V-ring 121, particularly to both lips 122 and 123, and it also suppresses excessive deformation and protrusion of the lips 122 and 123 that are caused by friction with the stem 510 and fluid pressure.

[0031] The clamping ring 160 includes a tapered inner peripheral surface 161 on the side that contacts the press ring 150, i.e., on the atmosphere side (left side in FIG. 1 ). The tapered inner peripheral surface 161 is inclined so that its diameter narrows from the atmosphere side end (left end in FIG. 1 ) of the clamping ring 160 toward the center in the axial direction. The maximum diameter of the tapered inner peripheral surface 161, i.e., the inner diameter at the atmosphere side end (left end in FIG. 1 ) of the clamping ring 160, is larger than the minimum diameter of the tapered outer peripheral surface 152 of the press ring 150, i.e., the outer diameter at the fluid side end (right end in FIG. 1 ) of the press ring 150. Therefore, the tapered inner peripheral surface 161 contacts the tapered outer peripheral surface 152. Meanwhile, the annular surface 162 on the fluid side (right side in FIG. 1 ) of the clamping ring 160 is in close contact with the annular surface 525 on the atmosphere side (left side in FIG. 1 ) of the rib 524 of the stuffing box 520. As a result, the pressing ring 150 is supported by the inner peripheral surface 523 and the ribs 524 of the stuffing box 520 via the fastening ring 160 . [Sealing action of shaft seal]

[0032] When the flange 533 of the packing gland 530 is pressed against the atmosphere-side end 522 of the stuffing box 520 by the axial force of the bolt 534, the fluid-side end 531 (left end in FIG. 1 ) of the packing gland 530 applies axial pressure (to the right in FIG. 1 ) to the annular surface 141 on the atmosphere side (left side in FIG. 1 ) of the female adapter 140. This pressure is transmitted by the recess 142 of the female adapter 140 to the heel 124 of the V ring 121 closest to the atmosphere (left side in FIG. 1 ), and is then transmitted by the lips 122, 123 of that V ring 121 to the heel 124 of the V ring 121 on the fluid side (right side in FIG. 1 ). Similar pressure transmission is repeated among the remaining V rings 121, causing the lips 122, 123 of the V ring 121 closest to the fluid side (right side in FIG. 1 ) to apply axial pressure (to the right in FIG. 1 ) to the protrusion 151 of the pressure ring 150. This pressure is applied by the tapered outer peripheral surface 152 of the pressing ring 150 to the tapered inner peripheral surface 161 of the clamping ring 160 , causing the clamping ring 160 to be pressed against the inner peripheral surface 523 and ribs 524 of the stuffing box 520 .

[0033] Since the stuffing box 520 is fixed to the casing 550 and has high rigidity, it is not substantially displaced or deformed by the pressure from the clamping ring 160. Therefore, the clamping ring 160 receives a strong reaction force in the axial direction (leftward in FIG. 1) from the inner peripheral surface 523 and ribs 524 of the stuffing box 520. Furthermore, this reaction force is applied to the V-packing 120 from the clamping ring 160 through the pressing ring 150. Therefore, the V-packing 120 receives both this reaction force and the pressure from the packing gland 530, and is compressed in the axial direction (left-right direction in FIG. 1) and expands in the radial direction (up-down direction in FIG. 1). Furthermore, the lips 122, 123 of each V-ring 121 are pushed and spread by the convex portion 151 of the pressing ring 150 or the heel 124 of the V-ring 121 on the fluid side (right side in FIG. 1), increasing the opening of the V-shape (the vertical distance in FIG. 1). As a result, the inner lip 122 of each V-ring 121 comes into close contact with the outer peripheral surface 511 of the stem 510, and the outer lip 123 comes into close contact with the inner peripheral surface 523 of the stuffing box 520. Therefore, only a very small amount of fluid can penetrate into the gap between the inner peripheral surface of the V-packing 120 and the outer peripheral surface 511 of the stem 510, and into the gap between the outer peripheral surface of the V-packing 120 and the inner peripheral surface 523 of the stuffing box 520. In this way, the gap between the stem 510 and the rib 524 of the stuffing box 520 is sealed.

[0034] The lips 122, 123 of the V ring 121 also have a self-sealing effect. When fluid is filled in the gap between the pressure ring 150 and the V ring 121, and further in the gaps between the V rings 121, the pressure of the fluid presses the inner lip 122 further against the outer peripheral surface 511 of the stem 510, and presses the outer lip 123 further against the inner peripheral surface 523 of the stuffing box 520. This further increases the sealing pressure at the lips 122, 123, especially at their tip ends, and therefore the sealing performance of the V packing 120 is high. [Prevents seal pressure from decreasing due to low temperatures]

[0035] When a valve handles a low-temperature fluid such as LNG or liquid nitrogen at or below one hundred and several tens of degrees below zero, the temperature of not only the stem 510 but also the shaft seal 100 decreases while the low-temperature fluid flows through the flow path 540 in the casing 550. Compared to the stem 510 and the stuffing box 520, the V-packing 120 experiences greater thermal contraction due to the decrease in temperature than the packing chamber. However, in the shaft seal 100, the pressure ring 150 and the clamping ring 160 also experience a decrease in temperature. As a result, despite the large difference in thermal contraction between the packing chamber and the V-packing 120, a decrease in seal pressure due to the decrease in temperature is prevented as follows.

[0036] 3A is a schematic diagram showing the force transmitted from the clamping ring 160 to the pressing ring 150 and then to the V ring 121 as the temperature drops. The clamping ring 160, like the V ring 121, is made of fluororesin, and therefore has a thermal shrinkage rate that is at least as high as that of the V ring 121. In contrast, the pressing ring 150 is made of metal, and therefore has a thermal shrinkage rate that is lower than that of either the V ring 121 or the clamping ring 160, and is only about 1 / 10 of that of either the V ring 121 or the clamping ring 160. Therefore, in the region where the tapered inner peripheral surface 161 of the clamping ring 160 contacts the tapered outer peripheral surface 152 of the pressing ring 150 (hereinafter referred to as the "clamping region"), the tapered inner peripheral surface 161 clamps the tapered outer peripheral surface 152 due to thermal shrinkage caused by the drop in temperature. In particular, the stress SS in the inner peripheral direction within the clamping ring 160 is transmitted from the tapered inner peripheral surface 161 to the tapered outer peripheral surface 152 as pressure PA. The tapered inner peripheral surface 161 and the tapered outer peripheral surface 152 are inclined so that the diameter increases as they approach the V ring 121 (toward the left in FIG. 3A), and therefore the pressure PA is inclined relative to the radial direction (the up-down direction in FIG. 3A). Therefore, stress is generated in the axial direction (toward the left in FIG. 3A) within the pressing ring 150, and this is transmitted as pressure PB in the axial direction (toward the left in FIG. 3A) from the convex portion 151 of the pressing ring 150 to the lips 122 and 123 of the V ring 121 that are positioned closest to the fluid (the rightmost side in FIG. 3A).

[0037] Meanwhile, the reaction force that tapered inner peripheral surface 161 receives from tapered outer peripheral surface 152 is also inclined relative to the radial direction, so axial stress (to the right in FIG. 3(a)) is also generated within clamping ring 160, and this stress is transmitted as axial pressure from clamping ring 160 to rib 524 of stuffing box 520. However, because rib 524 has sufficiently high rigidity, it is not substantially deformed or displaced by the axial pressure from clamping ring 160. Therefore, because clamping ring 160 cannot substantially displace in the axial direction, the pressure PB of pressing ring 150 against V ring 121 is sufficiently high.

[0038] This pressure PB is transmitted by the heel 124 of the V ring 121 to the lips 122, 123 of the adjacent V ring 121 on the atmosphere side (left side in Figure 3(a)). Similar transmission of pressure PB is repeated among the remaining V rings 121, and pressure PB is transmitted from the V ring 121 located closest to the atmosphere side (leftmost side in Figure 3(a)) to the female adapter 140. Because the female adapter 140 is supported by the packing gland 530, it cannot be substantially displaced by the pressure PB. Furthermore, because the female adapter 140 is made of metal and has higher rigidity than the V ring 121, it is not substantially deformed by the pressure PB. Therefore, each V ring 121 is displaced by the pressure PB toward the female adapter 140 (to the left in Figure 3(a)), and is further compressed in the axial direction due to the reaction force from the female adapter 140 against the pressure PB.

[0039] FIG. 3B is a schematic diagram showing the deformation of the V ring 121 and the displacement of the pressing ring 150 due to the thermal contraction of the clamping ring 160. The axial displacement of the V ring 121 is greater for V rings 121 closer to the pressing ring 150 (located to the right in FIG. 3B). In response to the displacement of the V ring 121, the pressing ring 150 also displaces toward the V packing 120 (to the left in FIG. 3B). At this time, due to the inclination of the tapered outer peripheral surface 152 and the tapered inner peripheral surface 161, the inner diameter of the clamping ring 160 contracts in response to the displacement of the pressing ring 150. Therefore, the clamping region is maintained, i.e., the tapered inner peripheral surface 161 continues to contact the tapered outer peripheral surface 152, so the pressing ring 150 continues to receive the pressure PA from the clamping ring 160, maintaining the pressure PB on the V packing 120. As a result, the axial compression of each V ring 121 is sufficiently large.

[0040] Each V-ring 121 increases its radial stress (vertical direction in FIG. 3B) as it is compressed in the axial direction, thus offsetting the decrease in radial stress due to the decrease in temperature. Furthermore, the lips 122, 123 of each V-ring 121 are expanded by the convex portion 151 of the pressing ring 150 or the heel 124 of the V-ring 121 on the fluid side (right side in FIG. 3B). Therefore, regardless of the decrease in temperature, the inner lip 122 maintains a sufficiently high sealing pressure PI against the outer peripheral surface 511 of the stem 510, and the outer lip 123 maintains a sufficiently high sealing pressure PO against the inner peripheral surface 523 of the stuffing box 520. [Advantages of embodiment 1]

[0041] In the shaft seal 100, the pressure ring 150 is fitted as a male adapter onto the lip side of the V-packing 120 and is supported by the inner peripheral surface 523 and rib 524 of the stuffing box 520 via the clamping ring 160. Therefore, at room temperature, the pressure ring 150 and the clamping ring 160 transmit the axial pressure from the stuffing box 520, which occurs when the stuffing box 520 and the packing gland 530 are joined, to the V-packing 120 essentially as is. This compresses the V-packing 120 axially, increasing the sealing pressure to a desired level. Meanwhile, at low temperatures, the clamping ring 160 thermally contracts to tighten the pressure ring 150, which in turn presses the V-packing 120 axially. This pressure PB further compresses the V-packing 120 axially, increasing radial stress. Therefore, the sealing pressure of the V-packing 120 remains sufficiently high, even at low temperatures. In this way, the shaft seal 100 can maintain the sealing pressure of the V-packing 120 at a sufficiently high level at low temperatures without excessively increasing it at room temperature.

[0042] Like V-packing 120, tightening ring 160 is also made of fluororesin, so the thermal shrinkage rate of tightening ring 160 is equal to or greater than that of V-packing 120. As a result, as the thermal shrinkage of V-packing 120 increases significantly, the pressure PB of pressing ring 150 increases due to the thermal shrinkage of tightening ring 160. Therefore, it is possible to effectively prevent a decrease in the sealing pressure of V-packing 120 due to lower temperatures.

[0043] Because the pressing ring 150 is made of metal, it has high rigidity against the pressure PA that the tapered outer peripheral surface 152 receives from the tapered inner peripheral surface 161 of the clamping ring 160, and is not substantially deformed even when subjected to the pressure PA. Therefore, the pressing ring 150 can slide along the stem 510 as smoothly even at low temperatures as it does at room temperature, and the pressure PA from the tapered inner peripheral surface can be efficiently converted into axial pressure PB on the V-packing 120.

[0044] The pressing ring 150 and the clamping ring 160 are located on the lip 122, 123 side of each V-ring 121. Therefore, the axial pressure PB of the pressing ring 150, which increases with the temperature drop, causes the lips 122, 123 of the V-ring 121 to open further, and presses them more firmly against the outer peripheral surface 511 of the stem 510 and the inner peripheral surface 523 of the stuffing box 520. As a result, the sealing performance of the V-packing 120 at low temperatures is further improved.

[0045] The pressing ring 150 and the tightening ring 160 are located on the opposite side of the packing gland 530 with respect to the V-packing 120. In this case, the pressure PB of the pressing ring 150, which increases with the temperature drop, is weakened by friction between each V-ring 121 and its surroundings 510, 110 before reaching the packing gland 530. Therefore, it is unlikely that the bolt 534 will be unable to withstand the pressure PB from the pressing ring 150 and loosen, and the packing gland 530 can return a sufficiently strong reaction force to the pressure PB. Therefore, each V-ring 121 is compressed sufficiently greatly by this reaction force and the pressure PB from the pressing ring 150, so that a sufficiently high sealing pressure is maintained. [Variations]

[0046] (1) The shaft seal 100 is used to seal the gap between the opening 551 of the casing 550 and the stem 510 of a valve. However, the shaft seal according to the embodiment of the present invention may also be used to seal the gap between the opening of the casing and the movable shaft of other fluid equipment. "Fluid equipment" includes not only devices that mechanically control fluid flow, such as valves, but also devices that change fluid pressure using power, such as pumps, and devices that generate power using fluid pressure, such as generators. "Casing" refers to a housing that houses a flow path inside, such as the main body of a pump, and "movable shaft" refers to a rod-shaped member that transmits power by rotating around a central axis or reciprocating along the central axis, such as the drive shaft of a pump. When the power is transmitted to a flow path within the casing, such as a pump impeller or piston, an opening is essential in the casing to allow the movable shaft to pass through. The shaft seal according to the embodiment of the present invention can also be used to reduce fluid leakage from this opening.

[0047] (2) The packing 120 is a V-packing made up of four V-rings 121. However, the present invention is not limited to this, and the number of V-rings 121 may be other than four, and spacer rings or V-rings made of a resin other than fluororesin may be inserted between the V-rings 121. All of the V-rings 121 may be made of a resin other than fluororesin. Furthermore, although the packing 120 is a V-packing, the present invention is not limited to this, and the packing may be another lip packing such as a U-packing, or a gland packing.

[0048] (3) The pressure ring 150 is made of metal. However, the present invention is not limited to this. The pressure ring may be made of a material other than metal, such as resin, as long as its thermal contraction rate is sufficiently lower than that of the clamping ring. Furthermore, it is desirable that the rigidity of the pressure ring is sufficiently high to withstand the pressure received from the clamping ring due to thermal contraction of the clamping ring. Furthermore, the pressure ring 150 also functions as a male adapter for the V-packing 120, but the present invention is not limited to this. The support body may include another annular member between the pressure ring and the V-packing that functions as a male adapter.

[0049] (4) The pressing ring 150 and the tightening ring 160 are located on the opposite side of the packing gland 530 with respect to the V packing 120. However, the present invention is not limited to this, and the pressing ring 150 and the tightening ring 160 may be located between the V packing 120 and the packing gland 530. It is sufficient that the packing gland 530 is fixed to the stuffing box 520 strongly enough that it will not be substantially displaced even when it receives axial pressure from the pressing ring 150 due to low temperatures.

[0050] (5) The pressing ring 150 and the tightening ring 160 are located on the opposite side of the packing gland 530 with respect to the V-packing 120. In this case, a spring may be incorporated into the packing gland 530 to prevent the V-packing 120 from reducing its sealing pressure due to stress relaxation at room temperature.

[0051] Figure 4 is a cross-sectional view of a modified shaft seal 200 according to embodiment 1. This modified shaft seal 200 differs from the shaft seal 100 shown in Figure 1 only in that it includes a spring 210. The other elements are common to the elements of shaft seal 100, so the explanation for embodiment 1 will be used for those elements.

[0052] Packing gland 530 is fixed to the atmospheric side end (left end in FIG. 4) 522 of stuffing box 520 by bolts 534 that pass through flange 533 parallel to stem 510 (left-right direction in FIG. 4). Springs 210 are, for example, coil springs, and one spring is provided for each bolt 534, coaxially surrounding the bolt 534. The springs are pressed against flange 533 by the axial force of nuts 535 that are screwed onto the bolts 534.

[0053] Even if the axial stress of V packing 120 decreases due to stress relaxation at room temperature, such as creep deformation or wear, packing gland 530 continues to apply axial pressure to V packing 120 due to the elasticity of spring 210. Therefore, the axial pressure from packing gland 530 further compresses V packing 120 in the axial direction, increasing radial stress. This offsets the decrease in radial stress due to stress relaxation, and the sealing pressure of V packing 120 is maintained high.

[0054] The pressing ring 150 and the tightening ring 160 are located on the opposite side of the packing gland 530 with respect to the V-packing 120. In this case, the pressure PB of the pressing ring 150, which increases with the temperature drop, is weakened by friction between each V-ring 121 and its surroundings 510, 110 before reaching the packing gland 530. Therefore, it is unlikely that the spring 210 will be unable to withstand the pressure PB from the pressing ring 150 and will further compress, and the packing gland 530 can return a sufficiently strong reaction force against the pressure PB. Therefore, each V-ring 121 is sufficiently compressed by this reaction force and the pressure PB from the pressing ring 150, so that a sufficiently high sealing pressure is maintained. Second Embodiment

[0055] Fig. 5(a) is a cross-sectional view of a shaft seal 300 according to a second embodiment of the present invention, Fig. 5(b) is a partially enlarged view of the packing 120 shown in Fig. 5(a) and its vicinity (the area surrounded by the dashed line in Fig. 5(a)), and Fig. 6 is an exploded view of supports 350, 360, and 370. The shaft seal 300 differs from the shaft seal 100 shown in Figs. 1 and 2 only in the configuration of the supports. The other elements are common to the elements of the shaft seal 100, so the explanation for the first embodiment will be used for those elements. -Support-

[0056] The support is composed of a male adapter 370, a pressing ring 350, and a stationary ring 360. The male adapter 370 is a circular member made of a metal such as bronze or aluminum bronze, and is adjacent to the fluid side of the V-packing 120 (the right side in FIG. 5 ) and coaxially surrounds the stem 510. The male adapter 370 has an inner diameter slightly larger than the diameter of the stem 510 and an outer diameter slightly smaller than the diameter of the inner circumferential surface 523 of the stuffing box 520, so that the sliding resistance against the stem 510 is sufficiently low and the pressing ring 350 can slide along the stem 510. The pressing ring 350 is a circular member made of a fluororesin such as PTFE, and is adjacent to the fluid side of the male adapter 370 (the right side in FIG. 5 ) and coaxially surrounds the stem 510. The inner diameter of the pressing ring 350 is larger than the diameter of the stem 510, so it does not apply sliding resistance to the stem 510, while its outer diameter is smaller than the diameter of the inner circumferential surface 523 of the stuffing box 520, so it is movable along the stem 510. The immovable ring 360 is an annular member made of a metal such as bronze or aluminum bronze, and is adjacent to the fluid side (the right side in FIG. 5 ) of the pressing ring 350, coaxially surrounding the stem 510. The inner diameter of the immovable ring 360 is slightly larger than the diameter of the stem 510, so it applies sufficiently low sliding resistance to the stem 510, while its outer diameter is equal to or greater than the diameter of the inner circumferential surface 523 of the stuffing box 520, so it is fixed to the inner circumferential surface 523 by press-fitting.

[0057] A series of annular projections 371 extend in the circumferential direction from the annular surface on the atmosphere side (left side in FIG. 5) of the male adapter 370, i.e., the side that comes into contact with the V packing 120. The projections 371 are fitted between the lips 122 and 123 of the V ring 121, which is located closest to the fluid side (right side in FIG. 5). Because the male adapter 370 is more rigid than the V ring 121, it transmits the axial pressure from the rib 524 of the stuffing box 520 that occurs when the stuffing box 520 and the packing gland 530 join together to the entire circumference of the V ring 121, particularly to both lips 122 and 123, without bias, and it also suppresses excessive deformation and extrusion of the lips 122 and 123 that may result from friction with the stem 510 or fluid pressure.

[0058] A tapered inner peripheral surface 352 is located on the inner peripheral portion of the pressure ring 350 on the fluid side (the right side in FIG. 5). The tapered inner peripheral surface 352 is inclined so that the diameter increases from the center of the pressure ring 350 in the axial direction toward the fluid side end (the right end in FIG. 5). The tapered inner peripheral surface 352 comes into contact with the stationary ring 360 (see below for details). As a result, the pressure ring 350 is supported by the inner peripheral surface 523 and ribs 524 of the stuffing box 520 via the stationary ring 360.

[0059] The stationary ring 360 includes a tapered outer peripheral surface 361 on the side that contacts the pressure ring 350, i.e., on the atmosphere side (left side in FIG. 1). The tapered outer peripheral surface 361 is inclined so that its diameter increases from the atmosphere-side end (left end in FIG. 5) of the stationary ring 360 toward the center in the axial direction. The minimum diameter of the tapered outer peripheral surface 361, i.e., the inner diameter at the atmosphere-side end (left end in FIG. 5) of the stationary ring 360, is smaller than the maximum diameter of the tapered inner peripheral surface 352 of the pressure ring 350, i.e., the outer diameter at the fluid-side end (right end in FIG. 5) of the pressure ring 350. Therefore, the tapered outer peripheral surface 361 contacts the tapered inner peripheral surface 352. Meanwhile, the annular surface 362 on the fluid side (right side in FIG. 5) of the stationary ring 360 is in close contact with the annular surface 525 on the atmosphere side (left side in FIG. 5) of the rib 524 of the stuffing box 520. As a result, the pressing ring 350 is supported by the inner peripheral surface 523 and the ribs 524 of the stuffing box 520 via the stationary ring 360 . [Sealing action of shaft seal]

[0060] Similar to the supports 150 and 160 of the first embodiment, the supports 350, 360, and 370 receive axial pressure (to the right in FIG. 5) from the packing gland 530 through the V-packing 120, transmit it to the inner circumferential surface 523 and ribs 524 of the stuffing box 520, and return a strong axial (to the left in FIG. 5) reaction force from them to the V-packing 120. As a result, the V-packing 120 is compressed in the axial direction (left-right direction in FIG. 5) and expands in the radial direction (up-down direction in FIG. 5), so that the lips 122 and 123 of each V-ring 121 come into close contact with the outer circumferential surface 511 of the stem 510 and the inner circumferential surface 523 of the stuffing box 520. In this way, the gap between the stem 510 and the ribs 524 of the stuffing box 520 is sealed. [Prevents seal pressure from decreasing due to low temperatures]

[0061] 7A is a schematic diagram showing the force transmitted between the supports 350, 360, and 370 and further to the V ring 121 as the temperature drops. The pressing ring 350 is made of fluororesin, just like the V ring 121, and therefore has a thermal shrinkage rate that is at least as high as that of the V ring 121. In contrast, the stationary ring 360 and the male adapter 370 are both made of metal, and therefore have a thermal shrinkage rate that is lower than that of either the V ring 121 or the pressing ring 350, specifically, only about 1 / 10 of that of either the V ring 121 or the pressing ring 350. Therefore, in the region where the tapered inner peripheral surface 352 of the pressing ring 350 contacts the tapered outer peripheral surface 361 of the stationary ring 360 (hereinafter referred to as the "clamping region"), the tapered inner peripheral surface 352 clamps the tapered outer peripheral surface 361 due to thermal shrinkage caused by the drop in temperature. In particular, the stress SS in the inner peripheral direction within the pressing ring 350 is transmitted from the tapered inner peripheral surface 352 to the tapered outer peripheral surface 361 as pressure PA. The tapered inner peripheral surface 352 and the tapered outer peripheral surface 361 are inclined so that their diameters narrow as they approach the V ring 121 (toward the left in FIG. 7A), and so both the pressure PA and the corresponding reaction force PR from the tapered outer peripheral surface 361 are inclined relative to the radial direction (the up-down direction in FIG. 7A). As a result, axial stress (to the left in FIG. 7A) is generated within the pressing ring 350, causing the pressing ring 350 to press the male adapter 370 in the axial direction (to the left in FIG. 7A). This pressure is transmitted from the protrusion 371 of the male adapter 370 to the lips 122 and 123 of the V ring 121, which are located closest to the fluid (the rightmost side in FIG. 7A), as pressure PB in the axial direction (to the left in FIG. 7A).

[0062] Meanwhile, the pressure exerted on the tapered outer peripheral surface 361 from the tapered inner peripheral surface 352 generates axial stress within the stationary ring 360 (to the right in FIG. 7A), which is transmitted as axial pressure from the stationary ring 360 to the rib 524 of the stuffing box 520. However, because both the stationary ring 360 and the rib 524 have sufficiently high rigidity, they are not substantially deformed or displaced. Therefore, the pressure PB of the male adapter 370 on the V ring 121 is sufficiently high. This pressure PB is transmitted to the female adapter 140 through each V ring 121. Because the female adapter 140 is not substantially displaced or distorted by the pressure PB, each V ring 121 is displaced toward the female adapter 140 by the pressure PB (to the left in FIG. 7A), and is further compressed in the axial direction by the reaction force from the female adapter 140 against the pressure PB.

[0063] FIG. 7B is a schematic diagram showing the displacement of the pressure ring 350 and the deformation of the V ring 121 due to thermal contraction. The axial displacement of the V ring 121 is greater for V rings 121 closer to the male adapter 370 (located to the right in FIG. 7B). In response to the displacement of the V ring 121, both the male adapter 370 and the pressure ring 350 displace toward the V packing 120 (to the left in FIG. 7B). At this time, due to the inclination of the tapered inner peripheral surface 352 and the tapered outer peripheral surface 361, the inner diameter of the pressure ring 350 contracts in response to the displacement of the pressure ring 350. Therefore, the clamping region is maintained, i.e., the tapered inner peripheral surface 352 continues to contact the tapered outer peripheral surface 361. Therefore, the pressure ring 350 continues to receive a reaction force PR against the pressure PA from the stationary ring 360, and the male adapter 370 maintains pressure PB on the V packing 120. As a result, the axial compression of each V ring 121 is sufficiently large.

[0064] Each V-ring 121 increases its radial stress (vertical direction in FIG. 7B) as it is compressed in the axial direction, offsetting the decrease in radial stress due to the decrease in temperature. Furthermore, the lips 122, 123 of each V-ring 121 are expanded by the convex portion 371 of the male adapter 370 or the heel 124 of the V-ring 121 on the fluid side (right side in FIG. 7B). Therefore, regardless of the decrease in temperature, the inner lip 122 maintains a sufficiently high sealing pressure PI against the outer peripheral surface 511 of the stem 510, and the outer lip 123 maintains a sufficiently high sealing pressure PO against the inner peripheral surface 523 of the stuffing box 520. [Advantages of Embodiment 2]

[0065] In the shaft seal 300, the pressure ring 350 is fitted onto the lip side of the V-packing 120 together with the male adapter 370, and is supported by the inner peripheral surface 523 and rib 524 of the stuffing box 520 via the stationary ring 360. Therefore, at room temperature, the pressure ring 350 and the stationary ring 360 transmit the axial pressure from the stuffing box 520, which is generated by the connection between the stuffing box 520 and the packing gland 530, to the V-packing 120 essentially as it is. This causes the V-packing 120 to compress axially, increasing the sealing pressure to a desired level. On the other hand, at low temperatures, the pressure ring 350 tightens the stationary ring 360 due to thermal contraction, and the corresponding reaction force PR from the stationary ring 360 causes the pressure ring 350 to press the male adapter 370 in the axial direction. This pressure PB further compresses the V-packing 120 in the axial direction, increasing radial stress, so that the sealing pressure of the V-packing 120 is maintained sufficiently high regardless of low temperatures. In this way, the shaft seal 300 can maintain the sealing pressure of the V-packing 120 sufficiently high at low temperatures without excessively increasing it at room temperature.

[0066] Like the V-packing 120, the pressure ring 350 is also made of fluororesin, so the thermal shrinkage rate of the pressure ring 350 is equal to or greater than that of the V-packing 120. As a result, the pressure PB associated with the thermal shrinkage of the pressure ring 350 increases as the thermal shrinkage of the V-packing 120 increases significantly. Therefore, it is possible to effectively prevent a decrease in the sealing pressure of the V-packing 120 due to lower temperatures.

[0067] Since the stationary ring 360 is made of metal, it has high rigidity against the pressure PA that the tapered outer peripheral surface 361 receives from the tapered inner peripheral surface 352 of the pressing ring 350, and does not substantially deform even when subjected to the pressure PA. Therefore, the tapered inner peripheral surface 352 can slide smoothly along the tapered outer peripheral surface 361, and the pressure PA from the tapered inner peripheral surface 352 can be efficiently converted into the axial pressure PB on the V-packing 120.

[0068] The pressing ring 350 and the stationary ring 360 are located on the lip 122, 123 side of each V ring 121. Therefore, the axial pressure PB of the pressing ring 350, which increases with the temperature drop, causes the lips 122, 123 of the V ring 121 to open further, and presses them more firmly against the outer peripheral surface 511 of the stem 510 and the inner peripheral surface 523 of the stuffing box 520. As a result, the sealing performance of the V packing 120 at low temperatures is further improved.

[0069] The pressing ring 350 and the stationary ring 360 are located on the opposite side of the packing gland 530 with respect to the V-packing 120. In this case, the pressure PB of the pressing ring 350, which increases with the temperature drop, is weakened by friction between each V-ring 121 and its surroundings 510, 110 before reaching the packing gland 530. Therefore, it is unlikely that the bolt 534 will be unable to withstand the pressure PB from the pressing ring 350 and loosen, and the packing gland 530 can return a sufficiently strong reaction force to the pressure PB. Therefore, each V-ring 121 is sufficiently compressed by the reaction force and the pressure PB from the pressing ring 350, so that a sufficiently high sealing pressure is maintained. [Variations]

[0070] The second embodiment can be modified in the same manner as the first embodiment. If the rigidity of the pressing ring 350 is sufficiently high, the male adapter 370 can be removed, and instead the end of the pressing ring 350 on the atmosphere side (the left end in FIG. 5) can be brought into direct contact with the V-ring 121 on the fluid side (the rightmost end in FIG. 5). [Explanation of symbols]

[0071] 100 Shaft seal 120 Gasket 121 V-ring 122 Inner Lip 123 outer lip 124 Heels 140 female adapter 141 Air-side torus of female adapter 142 Recess on the fluid side of the female adapter 150 Pressing ring 151 Convex part of pressure ring on the atmosphere side 152 Tapered outer surface of pressing ring 160 Clamping ring 161 Tapered inner surface of clamping ring 162 Fluid-side annular surface of clamping ring 510 stem 511 Stem outer surface 520 Stuffing Box 521 Fluid end of stuffing box 522 Atmospheric end of stuffing box 523 Inner surface of stuffing box 524 Ribs 525 Rib air side torus 530 Packing gland 531 Fluid side end of packing gland 532 Atmospheric end of packing gland 533 flange 534 volts 535 Nut 540 Flow path 550 casing 551 Casing opening 560 Casing external space

Claims

1. A shaft seal for sealing a gap between a movable shaft of a fluid device and a stuffing box, a resin packing that is filled into the gap by axial pressure from a packing gland; a support member which is an annular structure surrounding the movable shaft and has one axial side in contact with one end of the packing in the axial direction and the other side in contact with the stuffing box or the packing gland; Equipped with The support body has at least a portion in the axial direction. The outer periphery has a higher thermal shrinkage rate than the inner periphery, and the outer periphery tightens the inner periphery as the temperature drops. Including, The support body is configured such that the contact surface between the outer circumferential side and the inner circumferential side in the clamping region is inclined with respect to the radial direction, so that the force with which the outer circumferential side clamps the inner circumferential side is transmitted from the clamping region to the packing as axial pressure. A shaft seal characterized by:

2. A shaft seal for sealing a gap between a movable shaft of a fluid device and a stuffing box, a resin packing that is filled into the gap by axial pressure from a packing gland; a support member which is an annular structure surrounding the movable shaft and has one axial side in contact with one end of the packing in the axial direction and the other side in contact with the stuffing box or the packing gland; Equipped with The support is a clamping region located at least in a part in the axial direction, the clamping region having a higher thermal shrinkage rate on the outer circumferential side than on the inner circumferential side, and the outer circumferential side clamping the inner circumferential side as the temperature drops; a clamping ring which is an annular member surrounding the movable shaft and includes, on a side closer to the packing in the axial direction, a tapered inner circumferential surface which is inclined so that the diameter narrows from the end toward the center in the axial direction; a pressing ring which is an annular member surrounding the movable shaft, has a thermal shrinkage rate lower than that of the clamping ring, and includes, on the side farther from the packing in the axial direction, a tapered outer peripheral surface which is inclined so that the diameter narrows from the center toward the end in the axial direction; and The support is In the clamping region, the tapered inner peripheral surface contacts the tapered outer peripheral surface, The force with which the outer circumferential side clamps the inner circumferential side is transmitted from the clamped area to the packing as axial pressure. It is configured as follows: A shaft seal characterized by:

3. A shaft seal for sealing a gap between a movable shaft of a fluid device and a stuffing box, a resin packing that is filled into the gap by axial pressure from a packing gland; a support member which is an annular structure surrounding the movable shaft and has one axial side in contact with one end of the packing in the axial direction and the other side in contact with the stuffing box or the packing gland; Equipped with The support is a clamping region located at least in a part in the axial direction, the clamping region having a higher thermal shrinkage rate on the outer circumferential side than on the inner circumferential side, and the outer circumferential side clamping the inner circumferential side as the temperature drops; a pressing ring which is an annular member surrounding the movable shaft and includes, on a side farther from the packing in the axial direction, a tapered inner circumferential surface which is inclined so that the diameter increases from the center toward the end in the axial direction; a stationary ring which is an annular member surrounding the movable shaft, has a thermal shrinkage rate lower than that of the pressing ring, and includes, on the side closer to the packing in the axial direction, a tapered outer peripheral surface which is inclined so that the diameter increases from the end toward the center in the axial direction; and The support is In the clamping region, the tapered inner peripheral surface contacts the tapered outer peripheral surface, The force with which the outer circumferential side clamps the inner circumferential side is transmitted from the clamped area to the packing as axial pressure. It is configured as follows: A shaft seal characterized by:

4. The packing is a V-packing, The support is A male adapter that contacts one end of the packing in the axial direction having The shaft seal according to claim 2 or 3.

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