JP2023120568A - shaft seal - Google Patents

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 The present invention relates to shaft seals, and more particularly to those including resin packing.

A "shaft seal" is a part that seals the gap between the opening of the casing of a fluid device and the movable shaft, that is, a part that prevents fluid from leaking from the gap or foreign matter from entering the gap. is a generic term for Some shaft seals, in particular, include a packing that is packed in a stuffing box (see, for example, US Pat. A "stuffing box" is a cylindrical member fitted inside the opening of the casing, surrounding the movable shaft and forming an annular space, that is, a packing chamber, between the inner peripheral surface of itself and the outer peripheral surface of the movable shaft. Form. A "packing" is a string-like or annular flexible member that is typically packed in multiples into a packing chamber. In the packing chamber, a plurality of packings are arranged side by side along the movable shaft in a state where the packing is wound around the movable shaft if it is a string, or in a state that the movable shaft is passed through the inner side if the packing is ring-shaped. constitute a tubular structure surrounding the . When this cylindrical structure is axially compressed by an annular member called a "packing presser", it expands in the radial direction and comes into close contact with the inner peripheral surface of the stuffing box and the outer peripheral surface of the movable shaft. As a result, the packing chamber is closed, so that the gap between the opening of the casing and the movable shaft is sealed.

The pressure of the packing against the inner peripheral surface of the stuffing box and the outer peripheral surface of the movable shaft, that is, the sealing pressure, is the result of increased stress in the radial direction due to the axial compression of the packing. Therefore, when the packing undergoes a stress relaxation phenomenon due to creep deformation, wear, temperature drop, etc., the sealing pressure decreases. In order to prevent an increase in the amount of fluid leakage resulting from this decrease, an operation of increasing the pressure of the gland against the packing, that is, retightening, is required. As a device for reducing the frequency of retightening and reducing the burden of maintenance on the shaft seal, there is a known technique in which a spring that presses the packing in the axial direction is provided in the stuffing box or the packing retainer (for example, Patent Document 3- 6). As the packing reduces the axial stress by stress relief, it is further compressed axially under the pressure of the spring. Along with this, the stress in the radial direction of the packing increases, and the decrease due to stress relaxation is offset, so the sealing pressure is less likely to decrease.

Japanese Utility Model Laid-Open No. 02-084062 JP 2016-020711 A JP-A-11-344123 JP 2005-220832 A JP 2009-215905 A Japanese Patent No. 5820793

Resin is often selected as the packing material. In particular, fluororesins such as polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), and polyvinylidene fluoride (PVDF) have high heat resistance, excellent chemical stability against fluids, and friction against moving shafts. It is often used due to its low coefficient. However, resin, particularly fluororesin, has a thermal shrinkage rate about ten times higher than that of metal, which is commonly used as a material for movable shafts and stuffing boxes. Therefore, the use of a resin packing for the shaft seal has the following problems. "Thermal shrinkage rate" means the rate of thermal contraction of an object, that is, the rate at which the volume or length of the object decreases as the temperature drops, and is actually equal to the thermal expansion coefficient of the object. .

Liquid natural gas (LNG, boiling point about -160°C), liquid nitrogen (boiling point -196°C), liquid hydrogen (boiling point -253°C), liquid helium (boiling point -269°C), etc. , the fluid not only cools the movable shaft but also the shaft seal to a low temperature. Compared to movable shafts and stuffing boxes, which are generally made of metal, resin packing has a higher heat shrinkage rate, so it is possible to reduce the temperature from normal temperature (several tens of degrees below zero to several tens of degrees below zero) to low temperatures (hereinafter referred to as "low temperature ), the radial width of the packing is thermally shrunk to a greater extent than the radial inner dimension of the packing chamber. As a result, the sealing pressure is lowered particularly on the outer peripheral side of the packing. Furthermore, since there is a large difference in thermal shrinkage between the packing chamber and the packing, the degree of reduction in seal pressure due to lower temperatures is considerably greater than the degree of reduction due to relaxation of stress such as creep deformation and wear at room temperature.

Even if the packing is pressurized by a spring as in the shaft seals disclosed in Patent Documents 3 to 6, the pressure of the spring is only enough to prevent the seal pressure from decreasing due to stress relaxation of the packing at room temperature. However, it is not sufficient to prevent a decrease in seal pressure due to lower temperatures. However, it is difficult to pressurize the packing with a stronger spring, for reasons such as the need to reinforce or enlarge the structure of the stuffing box or packing gland. Even if a sufficiently strong spring were attached to the stuffing box or the like, the pressure of the spring would exceed the required height at room temperature, thus excessively increasing the sealing pressure of the packing. Therefore, the packing wears excessively fast, and the sliding resistance of the packing against the movable shaft is excessively high. In order to avoid these problems, it is necessary to devise a way to keep the pressure of the spring lower at room temperature than at low temperature. However, such ingenuity is also difficult.

SUMMARY OF THE INVENTION An 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 seal pressure at low temperatures without excessively increasing the seal pressure of the packing at room temperature. .

A shaft seal according to one aspect of the present invention is for sealing a gap between a movable shaft of a fluid device and a stuffing box, and includes 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 opposite side in contact with the stuffing box or packing gland. The support includes a tightening region at least partially in the axial direction. The outer peripheral side of the tightening region has a higher thermal contraction rate than the inner peripheral side, and the outer peripheral side tightens the inner peripheral side as the temperature drops. The support is configured such that this clamping force is transferred from the clamping area to the packing as an axial pressure.

The specific configuration of the support can vary. For example, the support may have a clamping ring and a pressure ring. The tightening 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 ends toward the center in the axial direction. The pressing ring is an annular member surrounding the movable shaft, has a lower thermal contraction rate than the tightening 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 toward 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.

Besides 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 remote from the packing in the axial direction. The tapered inner peripheral surface is inclined so that the diameter increases from the center toward the end in the axial direction. The stationary ring is an annular member surrounding the movable shaft, has a lower thermal contraction 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 ends toward the center in the axial direction. In the tightening region, the tapered inner peripheral surface of the pressing ring contacts the tapered outer peripheral surface of the stationary ring.

The packing may be a V-packing. Further, the support may have a male adapter that contacts one axial end of the packing. "V-packing" refers to a lip packing having a V-shaped cross section, that is, a molded packing (a packing formed by molding a material) including an overhanging portion called a "lip". In the V-packing, the two upper ends of the V-shaped cross section correspond to lips. "Male adapter" means a member that supports the V-packing from its lip side.

In the shaft seal according to the invention, the support is sandwiched axially between the gland and the packing or between the packing and the stuffing box. At ambient temperatures, the support substantially directly transfers axial pressure from the gland or stuffing box associated with 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 a packing gland or the like to the packing, but also exerts an axial pressure on the packing itself in the following manner.

During the flow of cold fluid through the casing of fluidic equipment, cooling occurs not only in the packing but also in the support. Along with this, the support transmits the force of the outer circumference of the tightening region tightening the inner circumference to the packing as an axial pressure. Specific configurations of the support are diverse, and include, for example, (1) a combination of a tightening ring and a pressing ring, and (2) a combination of a pressing ring and a stationary ring, as described above. .

(1) The pressing ring is sandwiched between the packing and the tightening ring in the axial direction, and the tapered outer peripheral surface is brought into contact with the tapered inner peripheral surface of the tightening ring. When the pressing ring is tightened by the tightening ring as the temperature drops, the tapered outer peripheral surface receives pressure from the tapered inner peripheral surface. Since the tapered outer peripheral surface and the tapered inner peripheral surface are inclined so that the diameter increases as the packing is approached, the pressure that the tapered outer peripheral surface receives from the tapered inner peripheral surface is inclined with respect to the radial direction. Therefore, an axial stress is generated in the pressing ring and transmitted from the pressing ring to the packing as an axial pressure. On the other hand, since the reaction force that the tapered inner peripheral surface receives from the tapered outer peripheral surface is also inclined with respect to the radial direction, an axial stress is also generated in the tightening ring, causing an axial stress from the tightening ring to the stuffing box or packing gland. transmitted as directional pressure. However, both the stuffing box and the packing gland are sufficiently rigid that axial pressure from the clamping ring will not substantially deform or displace them. As a result, the pressure ring against the packing is high, since the clamping ring cannot be substantially displaced axially.

(2) The pressing ring is sandwiched between the packing and the stationary ring in the axial direction, and the tapered inner peripheral surface is brought into contact with the tapered outer peripheral surface of the stationary ring. When the pressing ring tightens the stationary ring as the temperature drops, the tapered inner peripheral surface applies pressure to the tapered outer peripheral surface. Since the tapered inner peripheral surface and the tapered outer peripheral surface are inclined so that the diameter narrows toward the packing, the pressure applied by the tapered inner peripheral surface to the tapered outer peripheral surface is inclined with respect to the radial direction. Therefore, since the reaction force against the pressure is also inclined with respect to the radial direction, an axial stress is generated in the pressing ring and transmitted from the pressing ring to the packing as an axial pressure. On the other hand, due to the pressure applied by the tapered inner peripheral surface to the tapered outer peripheral surface, axial stress is also generated in the stationary ring, and is transmitted from the stationary ring to the stuffing box or packing gland as axial pressure. However, both the stuffing box and the gland are rigid enough that axial pressure from the stationary ring will not substantially deform or displace them. As a result, since the stationary ring cannot be substantially displaced axially, the pressure of the pressure ring against the packing is high.

Thus, at low temperatures the packing is subjected not only to axial pressure associated with the connection between the gland and the stuffing box, but also due to thermal contraction of the clamping area of the support. Therefore, the packing is further axially compressed, increasing the radial stress. This increase offsets the decrease in radial stress that accompanies the lowering of the packing temperature, making it possible to maintain a sufficiently high sealing pressure of the packing even at low temperatures. Thus, the above-described shaft seal according to the present invention can keep the sealing pressure of the packing sufficiently high at low temperatures without excessively increasing it at normal temperatures.

When the packing is a V-packing and the support includes the male adapter, the support is located on the lip side of the V-packing. Therefore, the axial pressure from the pressing ring, which increases as the temperature drops, not only compresses the V-packing axially, but also opens the lip of the V-packing further to press it against the stuffing box and the movable shaft even more strongly. . As a result, the sealing performance of the packing at low temperatures is further improved.

(a) is a cross-sectional view of a shaft seal according to Embodiment 1 of the present invention, and (b) is a partial enlarged view of the packing and its vicinity shown in (a). Figure 2 is an exploded view of the shaft seal shown in Figure 1; (a) is a schematic diagram showing the force transmitted from the tightening ring to the pressing ring and then to the packing as the temperature drops; Fig. 2 is a schematic diagram showing displacement; FIG. 4 is a cross-sectional view of a modification of the shaft seal according to Embodiment 1 of the present invention; (a) is a cross-sectional view of a shaft seal according to Embodiment 2 of the present invention, and (b) is a partially enlarged view of the packing and its vicinity shown in (a). Figure 6 is an exploded view of the support shown in Figure 5; (a) is a schematic diagram showing the force transmitted from the pressing ring to the stationary ring and the packing as the temperature decreases, and (b) is a schematic diagram showing the displacement of the pressing ring and the deformation of the packing due to thermal contraction of the pressing ring. It is a diagram.

A shaft seal according to an embodiment of the present invention is used, for example, to seal a gap between an opening of a valve casing and a stem. A “casing” is also called a “valve box” and is a housing that houses a flow path inside. A "stem" is also called a "valve stem", and is a rod-shaped member that transmits power to the valve body of a valve or the like by rotating around a central axis or reciprocating in the direction of the central axis. Since the power transmission destination is located in the flow path in the casing, the casing must have an opening for the stem to pass through. The shaft seal according to the embodiment of the present invention reduces the amount of fluid leakage from this opening.
<<Embodiment 1>>

FIG. 1(a) is a cross-sectional view of a shaft seal 100 according to Embodiment 1 of the present invention. Shaft seal 100 seals the gap between valve stem 510 and opening 551 in casing 550 . The cross section shown in FIG. 1( a ) includes the central axis of stem 510 . In FIG. 1(a), the central axis of the stem 510 is parallel to the left-right direction, the flow path 540 in the casing 550 is located on the right side, and the external space 560 of the casing 550 extends on the left side. are familiar with Hereinafter, the right side (that is, the side closer to the flow path 540) of an arbitrary portion shown in FIG. call.

A stuffing box 520 is fitted inside the opening 551 of the casing 550 . Stuffing box 520 is a cylindrical member made of metal such as brass, bronze, steel, or cast iron that coaxially surrounds stem 510 . The stuffing box 520 has a fluid-side end (right end in FIG. 1A) 521 facing a flow path 540 in the casing 550, and an atmosphere-side end (left end in FIG. 1A) 522. protrudes outside the casing 550 . The inner peripheral surface 523 of the stuffing box 520 forms a cylindrical packing chamber with the outer peripheral 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 peripheral surface 511 of the stem 510 to separate the flow path 540 from the packing chamber.

Inside the air side end (left end in FIG. 1) 522 of the stuffing box 520, the packing gland 530 is positioned at its fluid side end (right end in FIG. 1) 531 on the atmosphere side (left side in FIG. 1) of the packing chamber. ) is closed. Packing gland 530 is an annular member made of metal such as brass, bronze, steel, or cast iron that coaxially surrounds stem 510 . An annular flange 533 protrudes from an end portion (left end portion in FIG. 1) 532 on the atmosphere side of the packing retainer 530 in the outer peripheral direction. A plurality of bolts 534 pass through the flange 533 in parallel with the stem 510 (horizontal direction in FIG. 1) to fix the flange 533 to the air-side end 522 of the stuffing box 520 .
[Structure of Shaft Seal]

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

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 shown in FIG. 1(a)), and FIG. 1 is an exploded view of FIG. Packing 120 is a V-packing and is composed of, for example, four V-rings 121 . "V-ring" means a V-packing that forms a single annulus. Hereinafter, in order to avoid confusion with "V-ring", "V-packing" is used only as the general name of the V-ring packed in the packing chamber.

Each of the V-rings 121 is an annular molded packing made of fluororesin such as PTFE. character shape. The two upper ends of the V-shape, that is, the lips 122 and 123 protrude to one side (the right side in FIG. 1) of the V-ring 121 in the axial direction and are connected in the circumferential direction of the V-ring 121 to form two concentric rings. The inner lip 122 has a minimum inner diameter less than the diameter of the stem 510 , and the outer lip 123 has a maximum outer diameter greater than the diameter of the inner peripheral surface 523 of the stuffing box 520 . The flexibility of their material allows the lips 122, 123 to bend to increase or decrease the V-shaped opening (vertical spacing in FIG. 1). A V-shaped lower end portion 124 (hereinafter referred to as “heel”) protrudes to the opposite side (to the left in FIG. 1) of the lips 122 and 123 in the axial direction of the V-ring 121 and continues in the circumferential direction of the V-ring 121 . form a single ring. The cross section of the heel 124 is tapered in the axial direction of the V-ring 121, and in particular, the inner diameter widens and the outer diameter narrows toward the tip. The four V-rings 121 are pushed into the packing chamber with the lips 122 and 123 facing the fluid side (right side in FIG. 1) and coaxially passing the stem 510 inside, and are placed side by side along the stem 510. be sorted by At this time, the heel 124 of another V-ring 121 adjacent to the fluid side (right side 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 or V-packing 120 .
－Female Adapter－

Female adapter 140 is an annular member made of metal such as bronze or aluminum bronze, and coaxially surrounds stem 510 adjacent to the air side (left side in FIG. 1) of V-packing 120 . The female adapter 140 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 peripheral surface 523 of the stuffing box 520 . Thereby, the female adapter 140 has sufficiently low sliding resistance against the stem 510 and can slide along the stem 510 .

A "female adapter" originally refers to a member 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, that is, from the atmosphere side (left side in FIG. 1). In fact, the atmosphere side (left side in FIG. 1) annular surface 141 of the female adapter 140 contacts the fluid side end (right side in FIG. 1) 531 of the gland 530 . On the other hand, on the fluid side (right side in FIG. 1) of the female adapter 140, that is, on the side that contacts the V-packing 120, there is an annular concave portion 142 extending in the circumferential direction. The heel 124 of the V-ring 121 positioned 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 a higher rigidity than the V-ring 121, the tight contact with the heel 124 allows the pressure from the packing retainer 530 to be evenly transmitted to the entire periphery of the heel 124, and resists friction with the stem 510 and fluid pressure. This suppresses the resulting excessive deformation and protrusion of the heel 124. - 特許庁
-Support-

FIG. 2 includes an exploded view of the supports 150,160. The support consists of a pressure ring 150 and a clamping ring 160 . The pressure ring 150 is an annular member made of metal such as bronze or aluminum bronze, and coaxially surrounds the stem 510 adjacent to the fluid side (right side in FIG. 1) of the V-packing 120 . Since the pressing 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 peripheral surface 523 of the stuffing box 520, the sliding resistance against the stem 510 is sufficiently low and the stem Sliding along 510 is possible. The tightening ring 160 is an annular member made of fluororesin such as PTFE, and coaxially surrounds the stem 510 adjacent to the fluid side (right side in FIG. 1) of the pressing ring 150 . Since the tightening ring 160 has an inner diameter larger than the diameter of the stem 510 , it does not give sliding resistance to the stem 510 . It is fixed to surface 523 by press fitting.

The pressing ring 150 functions as a male adapter for the V-packing 120. In fact, from the annular surface on the atmosphere side (left side in FIG. 1) of the pressing ring 150 , that is, the side that contacts the V-packing 120 , an annular projection 151 that is continuous in the circumferential direction protrudes. The convex portion 151 is fitted between the lips 122 and 123 of the V-ring 121 positioned closest to the fluid side (right side in FIG. 1). On the other hand, there is a tapered outer peripheral surface 152 on the outer peripheral portion on the fluid side (right side in FIG. 1) of the pressing ring 150 . The tapered outer peripheral surface 152 is inclined so that the diameter decreases from the center in the axial direction of the pressing ring 150 toward the fluid-side end (the right end in FIG. 1). The tapered outer peripheral surface 152 contacts the clamping ring 160 (see below for details). As a result, the pressing ring 150 is supported by the inner peripheral surface 523 of the stuffing box 520 and the ribs 524 via the tightening ring 160 . Because the pressure ring 150 is stiffer than the V-ring 121, the axial pressure from the ribs 524 of the stuffing box 520 associated with the coupling between the stuffing box 520 and the gland 530 is directed to the entire circumference of the V-ring 121, particularly The transmission is evenly distributed to both lips 122 and 123, and excessive deformation and protrusion of the lips 122 and 123 due to friction with the stem 510 and fluid pressure are suppressed.

The tightening ring 160 includes a tapered inner peripheral surface 161 on the side that contacts the pressing ring 150, ie, the atmosphere side (left side in FIG. 1). The tapered inner peripheral surface 161 is inclined so that the diameter of the tightening ring 160 decreases from the atmosphere-side end (the left end in FIG. 1) toward the center in the axial direction. The maximum diameter of the tapered inner peripheral surface 161, that is, the inner diameter of the end of the clamping ring 160 on the atmosphere side (the left end in FIG. 1) is the minimum diameter of the tapered outer peripheral surface 152 of the pressing ring 150, that is, the end of the pressing ring 150 on the fluid side ( It is larger than the outer diameter of the right end in FIG. Therefore, the tapered inner peripheral surface 161 contacts the tapered outer peripheral surface 152 . On the other hand, the annular surface 162 on the fluid side (right side in FIG. 1) of the tightening 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 of the stuffing box 520 and the ribs 524 via the tightening ring 160 .
[Sealing action of shaft seal]

When the flange 533 of the packing gland 530 is pressed against the air side end 522 of the stuffing box 520 by the axial force of the bolt 534 , the fluid side end (left end in FIG. An axial pressure (rightward in FIG. 1) is applied to the annular surface 141 on the atmosphere side (leftward in FIG. 1). This pressure is transmitted to the heel 124 of the V-ring 121 closest to the atmosphere (left side in FIG. 1) by the recess 142 of the female adapter 140, and further to the fluid side (right side in FIG. 1) by the lips 122 and 123 of the V-ring 121. It is transmitted to the heel 124 of the V ring 121 . Similar transmission of pressure is repeated between the remaining V-rings 121 so that the lips 122 and 123 of the V-ring 121 closest to the fluid side (the right side in FIG. 1) move axially against the projection 151 of the pressing ring 150 . (Right direction in FIG. 1) pressure is applied. Since this pressure is applied by the tapered outer peripheral surface 152 of the pressing ring 150 against the tapered inner peripheral surface 161 of the tightening ring 160 , the tightening ring 160 is pressed against the inner peripheral surface 523 of the stuffing box 520 and the ribs 524 .

Because the stuffing box 520 is fixed to the casing 550 and rigid, the pressure from the clamping ring 160 does not substantially displace or deform it. Therefore, the tightening ring 160 receives a strong reaction force in the axial direction (left direction in FIG. 1) from the inner peripheral surface 523 of the stuffing box 520 and the ribs 524 . Furthermore, since this reaction force is applied from the tightening ring 160 to the V-packing 120 through the pressing ring 150, the V-packing 120 receives both this reaction force and the pressure from the packing retainer 530 in the axial direction (horizontal direction in FIG. 1). ) and expands in the radial direction (vertical direction in FIG. 1). Furthermore, the lips 122 and 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) to form a V-shaped opening (up and down in FIG. 1). direction spacing). As a result, the inner lip 122 of each V-ring 121 contacts the outer peripheral surface 511 of the stem 510 , and the outer lip 123 contacts 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 V-packing 120 and the outer peripheral surface 511 of the stem 510 and the gap between the outer peripheral surface of the V-packing 120 and the inner peripheral surface 523 of the stuffing box 520. . Thus, the gap between the stem 510 and the rib 524 of the stuffing box 520 is sealed.

Lips 122, 123 of V-ring 121 are also self-sealing. When the gap between the pressing ring 150 and the V ring 121 and the gap between the V rings 121 are filled with fluid, the inner lip 122 is further pressed against the outer peripheral surface 511 of the stem 510 by the pressure of the fluid, and the outer lip 122 is pressed further. The lip 123 is further pressed against the inner peripheral surface 523 of the stuffing box 520 . As a result, the sealing pressure of the lips 122 and 123, especially their tip portions, is further increased, so that the sealing performance of the V-packing 120 is high.
[Preventive action against reduction in seal pressure due to low temperature]

When the valve handles a low-temperature fluid such as LNG or liquid nitrogen, which is below 100°C below zero, not only the stem 510 but also the shaft seal 100 is cooled while the low-temperature fluid flows through the passage 540 in the casing 550. occurs. Since the V-packing 120 has a higher thermal contraction rate than the stem 510 and the stuffing box 520, the V-packing 120 undergoes greater thermal shrinkage than the packing chamber due to lower temperatures. However, in the shaft seal 100, lower temperatures also occur in the compression ring 150 and the clamping ring 160. FIG. As a result, regardless of the large difference in thermal contraction between the packing chamber and the V-packing 120, a drop in seal pressure due to lower temperatures is prevented as follows.

FIG. 3(a) is a schematic diagram showing the force transmitted from the tightening ring 160 to the pressing ring 150 and then to the V ring 121 as the temperature decreases. Since the tightening ring 160 is made of fluororesin like the V-ring 121, its thermal contraction rate is as high as that of the V-ring 121 or higher. On the other hand, since the pressing ring 150 is made of metal, its heat shrinkage rate is lower than that of both the V ring 121 and the tightening ring 160, especially about 1/10. Therefore, in the area where the tapered inner peripheral surface 161 of the tightening ring 160 contacts the tapered outer peripheral surface 152 of the pressing ring 150 (hereinafter referred to as "tightening area"), the tapered inner peripheral surface is 161 tightens the tapered outer peripheral surface 152 , and in particular, the stress SS in the inner peripheral direction in the tightening ring 160 is transmitted from the tapered inner peripheral surface 161 to the tapered outer peripheral surface 152 as pressure PA. Since 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), the pressure PA increases in the radial direction (Fig. 3 (a) is inclined with respect to the vertical direction). Therefore, a stress in the axial direction (leftward in FIG. 3A) is generated in the pressing ring 150, and the stress is exerted from the convex portion 151 of the pressing ring 150 to the fluid side (rightmost in FIG. 3A). The pressure PB is transmitted to the lips 122 and 123 of the V-ring 121 in the axial direction (left direction in FIG. 3(a)).

On the other hand, since the reaction force that the tapered inner peripheral surface 161 receives from the tapered outer peripheral surface 152 is also inclined with respect to the radial direction, stress in the axial direction (right direction in FIG. 3(a)) is applied to the tightening ring 160 as well. generated and transmitted from the clamping ring 160 to the ribs 524 of the stuffing box 520 as axial pressure. However, ribs 524 are stiff enough that axial pressure from clamping ring 160 does not substantially deform or displace them. Therefore, the pressure PB of the pressing ring 150 against the V-ring 121 is sufficiently high since the fastening ring 160 cannot be substantially displaced in the axial direction.

This pressure PB is transmitted by the heel 124 of the V-ring 121 to the lips 122 and 123 of the V-ring 121 adjacent to the atmosphere side (left side in FIG. 3(a)). A similar transmission of pressure PB is repeated between the remaining V-rings 121 , whereby pressure PB is transmitted from the V-ring 121 located closest to the atmosphere (leftmost in FIG. 3( a )) to the female adapter 140 . Since the female adapter 140 is supported by the gland 530, it cannot be substantially displaced by the pressure PB. Furthermore, since the female adapter 140 is made of metal and is stiffer than the V-ring 121, it does not substantially deform under the pressure PB. Therefore, each V ring 121 is displaced toward the female adapter 140 (to the left in FIG. 3(a)) by the pressure PB, and further compressed in the axial direction by receiving the reaction force from the female adapter 140 against the pressure PB. be.

FIG. 3B is a schematic diagram showing deformation of the V ring 121 and displacement of the pressing ring 150 due to thermal contraction of the tightening ring 160 . The displacement of the V ring 121 in the axial direction is greater for the V ring 121 closer to the pressing ring 150 (located on the right side in FIG. 3(b)). As the V-ring 121 is displaced, the pressing ring 150 is also displaced toward the V-packing 120 (leftward in FIG. 3(b)). 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 tightening ring 160 is reduced according to the displacement of the pressing ring 150 . Therefore, the tightening area is maintained, that is, the tapered inner peripheral surface 161 continues to contact the tapered outer peripheral surface 152, so that the pressure ring 150 continues to receive the pressure PA of the tightening ring 160 and maintain the pressure PB against the V-packing 120. . As a result, the axial compression of each V-ring 121 is sufficiently large.

Since each V-ring 121 increases the stress in the radial direction (vertical direction in FIG. 3(b)) as it is compressed in the axial direction, the decrease due to the temperature decrease is offset. Furthermore, the lips 122 and 123 of each V-ring 121 are spread by the protrusion 151 of the pressing ring 150 or the heel 124 of the V-ring 121 on the fluid side (right side in FIG. 3(b)). Therefore, regardless of the temperature drop, 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. keep high.
[Advantages of Embodiment 1]

In shaft seal 100 , pressing ring 150 is fitted as a male adapter to the lip side of V-packing 120 and supported by inner peripheral surface 523 and ribs 524 of stuffing box 520 via tightening ring 160 . Therefore, at room temperature, the force ring 150 and the clamp ring 160 substantially directly transmit the axial pressure from the stuffing box 520 associated with the coupling between the stuffing box 520 and the gland 530 to the V-packing 120 . This axially compresses the V-packing 120 and raises the sealing pressure to the desired height. On the other hand, at low temperatures, the tightening ring 160 tightens the pressing ring 150 by thermal contraction, and the pressing ring 150 axially presses the V-packing 120 accordingly. Since the V-packing 120 is further compressed in the axial direction by this pressure PB to increase the stress in the radial direction, the sealing pressure of the V-packing 120 is maintained sufficiently high regardless of the temperature drop. 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.

Since the tightening ring 160 is also made of fluororesin like the V-packing 120, the heat shrinkage rate of the tightening ring 160 is equal to or higher than the heat shrinkage rate of the V-packing 120. As a result, the thermal contraction of V-packing 120 significantly increases, and the pressure PB of pressing ring 150 increases due to the thermal contraction of tightening ring 160 . Therefore, it is possible to effectively prevent the sealing pressure of the V-packing 120 from decreasing as the temperature drops.

Since the pressing ring 150 is made of metal, the tapered outer peripheral surface 152 has high rigidity against the pressure PA received from the tapered inner peripheral surface 161 of the tightening ring 160, and does not substantially deform even when receiving the pressure PA. Therefore, since the pressing ring 150 can slide along the stem 510 as smoothly as at room temperature even at a low temperature, the pressure PA from the tapered inner peripheral surface can be efficiently converted into the axial pressure PB to the V-packing 120. can.

A compression ring 150 and a clamping ring 160 are located on the lips 122 , 123 side of each V-ring 121 . Therefore, the axial pressure PB of the pressing ring 150, which rises as the temperature drops, causes the lips 122 and 123 of the V-ring 121 to open further, causing the outer peripheral surface 511 of the stem 510 and the inner peripheral surface 523 of the stuffing box 520 to open. Press harder. As a result, the sealing performance of the V-packing 120 at low temperatures is even higher.

The pressing ring 150 and the tightening ring 160 are located on the opposite side of the V-packing 120 from the packing gland 530 . In this case, the pressure PB of the pressing ring 150, which rises as the temperature drops, reaches the packing gland 530 after being weakened by the friction between each V-ring 121 and its surroundings 510, 110. FIG. Therefore, it is unlikely that the bolt 534 will loosen due to the pressure PB from the pressing ring 150, so the packing gland 530 can return a sufficiently strong reaction force against the pressure PB. Therefore, each V-ring 121 is sufficiently compressed by the reaction force and the pressure PB from the pressing ring 150, so that the sealing pressure is maintained sufficiently high.
[Modification]

(1) The shaft seal 100 is used to seal the gap between the opening 551 of the valve casing 550 and the stem 510 . However, the shaft seal according to the embodiment of the present invention may be used for sealing the gap between the opening of the casing of other fluid equipment and the movable shaft. In addition to valves and other devices that mechanically control the flow of fluid, “fluid devices” include pumps and other devices that use power to change fluid pressure, and generators and other devices that use fluid pressure to drive power. It includes the equipment that produces it. “Casing” means a housing such as a main body of a pump that houses a flow path inside. means a rod-shaped member that transmits When the power transmission destination is located in the flow path in the casing, such as the impeller or piston of a pump, the casing must have an opening for the movable shaft to pass through. The shaft seal according to the embodiment of the present invention can also be used for the purpose of suppressing the amount of fluid leakage from this opening.

(2) The packing 120 is a V-packing composed 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. may All of the V-rings 121 may be made of a resin other than fluororesin. Also, the packing 120 is a V-packing, but the present invention is not limited to this, and the packing may be other lip packing such as a U-packing, or a gland packing.

(3) The pressing ring 150 is made of metal. However, the present invention is not limited to this, and the pressing ring may be made of a material different from metal, such as resin, as long as its thermal shrinkage is sufficiently lower than that of the tightening ring. Furthermore, it is desirable that the rigidity of the pressing ring is sufficiently high with respect to the pressure received from the tightening ring due to thermal contraction of the tightening ring. Also, the pressing ring 150 also functions as a male adapter for the V-packing 120, but the present invention is not limited to this. The support may include another annular member between the pressure ring and the V-packing, which functions as a male adapter.

(4) The pressing ring 150 and the tightening ring 160 are located on the opposite side of the V-packing 120 from the packing retainer 530 . However, the present invention is not limited to this, and the compression ring 150 and the clamping ring 160 may be arranged between the V-packing 120 and the gland 530 . It is sufficient that the packing retainer 530 is firmly fixed to the stuffing box 520 to such an extent that it does not substantially displace even if it receives the axial pressure of the pressing ring 150 due to the decrease in temperature.

(5) The pressing ring 150 and the tightening ring 160 are located on the opposite side of the V-packing 120 from the packing retainer 530 . In this case, a spring may be incorporated into the packing follower 530 for the purpose of preventing the V-packing 120 from reducing the sealing pressure as the stress relaxes at room temperature.

4 is a cross-sectional view of a modification 200 of the shaft seal according to Embodiment 1. FIG. This variant 200 differs from the shaft seal 100 shown in FIG. 1 only in that it includes a spring 210 . Other elements are the same as those of the shaft seal 100, so the description of the first embodiment is used.

The packing retainer 530 is fixed to the atmospheric side end (the left end in FIG. 4) 522 of the stuffing box 520 by a bolt 534 passing through the flange 533 in parallel with the stem 510 (horizontal direction in FIG. 4). be. The springs 210 are, for example, coil springs, and are arranged on each bolt 534 so as to coaxially surround the bolt 534 and are pressed against the flange 533 by the axial force of a nut 535 screwed onto the bolt 534 .

Even if V-packing 120 reduces the stress in the axial direction due to stress relaxation at normal temperature such as creep deformation or wear, packing retainer 530 continues to press V-packing 120 in the axial direction due to the elasticity of spring 210 . Thus, the axial pressure from the gland 530 compresses the V-packing 120 further in the axial direction, increasing the radial stress. As a result, the reduction in radial stress due to stress relaxation is offset, so the sealing pressure of V-packing 120 is maintained high.

The pressing ring 150 and the tightening ring 160 are located on the opposite side of the V-packing 120 from the packing gland 530 . In this case, the pressure PB of the pressing ring 150, which rises as the temperature drops, reaches the packing gland 530 after being weakened by the friction between each V-ring 121 and its surroundings 510, 110. FIG. Therefore, the possibility that the spring 210 cannot withstand the pressure PB from the pressing ring 150 and further shrinks is low, so that the packing retainer 530 can return a sufficiently strong reaction force against the pressure PB. Therefore, each V-ring 121 is sufficiently compressed by the reaction force and the pressure PB from the pressing ring 150, so that the sealing pressure is maintained sufficiently high.
<<Embodiment 2>>

FIG. 5(a) is a cross-sectional view of a shaft seal 300 according to Embodiment 2 of the present invention, and FIG. 5(b) is a packing 120 shown in FIG. ), and FIG. 6 is an exploded view of supports 350, 360, and 370. FIG. The shaft seal 300 differs from the shaft seal 100 shown in FIGS. 1 and 2 only in the structure of the support. Other elements are the same as those of the shaft seal 100, so the description of the first embodiment is used.
-Support-

The support consists of a male adapter 370 , a compression ring 350 and a stationary ring 360 . Male adapter 370 is an annular member made of metal such as bronze or aluminum bronze, and coaxially surrounds stem 510 adjacent the fluid side (right side in FIG. 5) of V-packing 120 . Since 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 peripheral surface 523 of the stuffing box 520, the sliding resistance to the stem 510 is sufficiently low and the stem Sliding along 510 is possible. The pressing ring 350 is an annular member made of fluororesin such as PTFE, and coaxially surrounds the stem 510 adjacent to the fluid side (right side in FIG. 5) of the male adapter 370 . Since the pressing ring 350 has an inner diameter larger than the diameter of the stem 510 , it does not provide sliding resistance to the stem 510 , while its outer diameter is smaller than the diameter of the inner peripheral surface 523 of the stuffing box 520 , so that the pressure ring 350 slides along the stem 510 . displacement is possible. The stationary ring 360 is an annular member made of metal such as bronze or aluminum bronze and coaxially surrounds the stem 510 adjacent to the fluid side (right side in FIG. 5) of the pressure ring 350 . Since the stationary ring 360 has an inner diameter slightly larger than the diameter of the stem 510, the sliding resistance against the stem 510 is sufficiently low. It is fixed to the inner peripheral surface 523 by press fitting.

An annular projection 371 extending in the circumferential direction protrudes from the annular surface on the atmosphere side (left side in FIG. 5 ) of the male adapter 370 , that is, the side that contacts the V-packing 120 . The convex portion 371 is fitted between the lips 122 and 123 of the V-ring 121 positioned closest to the fluid side (right side in FIG. 5). Because the male adapter 370 is stiffer than the V-ring 121, the axial pressure from the ribs 524 of the stuffing box 520 associated with the coupling between the stuffing box 520 and the gland 530 is directed to the entire circumference of the V-ring 121, particularly The transmission is evenly distributed to both lips 122 and 123, and excessive deformation and protrusion of the lips 122 and 123 due to friction with the stem 510 and fluid pressure are suppressed.

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

The stationary ring 360 includes a tapered outer peripheral surface 361 on the side that contacts the pressing ring 350, that is, on the atmosphere side (left side in FIG. 1). The tapered outer peripheral surface 361 is inclined so that the diameter increases from the air-side end (the 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, that is, the inner diameter of the end of the stationary ring 360 on the atmosphere side (left end in FIG. 5 is smaller than the outer diameter of the right end). Therefore, the tapered outer peripheral surface 361 contacts the tapered inner peripheral surface 352 . On the other hand, 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 of the stuffing box 520 and the ribs 524 via the stationary ring 360 .
[Sealing action of shaft seal]

Supports 350 , 360 , 370 receive pressure in the axial direction (right direction in FIG. 5 ) from packing retainer 530 through V-packing 120 in the same way as supports 150 , 160 according to the first embodiment, and are pushed inside stuffing box 520 . It is transmitted to the peripheral surface 523 and the rib 524 , and a strong reaction force from them in the axial direction (left direction in FIG. 5 ) is returned to the V-packing 120 . As a result, the V-packing 120 is compressed in the axial direction (horizontal direction in FIG. 5) and expands in the radial direction (vertical direction in FIG. 5). It adheres to the inner peripheral surface 523 of the stuffing box 520 . Thus, the gap between the stem 510 and the rib 524 of the stuffing box 520 is sealed.
[Preventive action against reduction in seal pressure due to low temperature]

FIG. 7(a) is a schematic diagram showing forces transmitted between the supports 350, 360, 370 and further to the V-ring 121 as the temperature decreases. Like the V-ring 121, the pressing ring 350 is made of fluororesin, and therefore has a heat shrinkage rate that is as high as or higher than that of the V-ring 121. As shown in FIG. On the other hand, since both the stationary ring 360 and the male adapter 370 are made of metal, the thermal contraction rate thereof is lower than that of both the V ring 121 and the pressing ring 350, in particular only about 1/10. Therefore, in a 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 a “tightening region”), the tapered inner peripheral surface 352 is deformed due to thermal contraction due to the decrease in temperature. clamps the tapered outer peripheral surface 361, and in particular, the stress SS in the inner peripheral direction in the pressing ring 350 is transmitted from the tapered inner peripheral surface 352 to the tapered outer peripheral surface 361 as a pressure PA. Since the tapered inner peripheral surface 352 and the tapered outer peripheral surface 361 are inclined so that the diameter becomes narrower as they approach the V-ring 121 (toward the left in FIG. 7A), the pressure PA The reaction force PR from the outer peripheral surface 361 is also inclined with respect to the radial direction (vertical direction in FIG. 7A). Therefore, since a stress in the axial direction (left direction in FIG. 7(a)) is generated in the pressing ring 350, the pressing ring 350 presses the male adapter 370 in the axial direction (left direction in FIG. 7(a)). . This pressure is applied from the convex portion 371 of the male adapter 370 to the lips 122 and 123 of the V-ring 121 located on the fluid side (rightmost in FIG. 7(a)) in the axial direction (leftward in FIG. 7(a)). ) is transmitted as the pressure PB.

On the other hand, due to the pressure applied from the tapered inner peripheral surface 352 to the tapered outer peripheral surface 361 , a stress in the axial direction (right direction in FIG. 7A ) is also generated in the stationary ring 360 , and the stationary ring 360 depresses the stuffing box 520 . Axial pressure is transmitted to ribs 524 . However, both the stationary ring 360 and the ribs 524 are rigid enough that they do not substantially deform or displace. Therefore, the pressure PB of male adapter 370 against V-ring 121 is sufficiently high. This pressure PB is transmitted through each V-ring 121 to the female adapter 140 . Since the female adapter 140 is substantially neither displaced nor deformed by the pressure PB, each V-ring 121 is displaced toward the female adapter 140 by the pressure PB (to the left in FIG. It is further compressed in the axial direction by receiving a reaction force from 140 .

FIG. 7B is a schematic diagram showing the displacement of the pressing 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 the V-ring 121 closer to the male adapter 370 (located on the right side in FIG. 7(b)). As the V-ring 121 is displaced, both the male adapter 370 and the pressing ring 350 are displaced toward the V-packing 120 (leftward in FIG. 7(b)). 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 pressing ring 350 is reduced in accordance with the displacement. Therefore, since the tightening area is maintained, that is, the tapered outer peripheral surface 361 continues to contact the tapered inner peripheral surface 352, the pressing ring 350 continues to receive the reaction force PR against the pressure PA from the stationary ring 360, and the male adapter 370 is connected to the V-packing. Maintain pressure PB against 120; As a result, the axial compression of each V-ring 121 is sufficiently large.

Since each V ring 121 increases the stress in the radial direction (vertical direction in FIG. 7(b)) as it is compressed in the axial direction, the decrease due to the temperature decrease is offset. Furthermore, the lips 122 and 123 of each V-ring 121 are spread 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. 7(b)). Therefore, regardless of the temperature drop, 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. keep high.
[Advantages of Embodiment 2]

In shaft seal 300 , pressing ring 350 is fitted to the lip side of V-packing 120 together with male adapter 370 , and is supported by inner peripheral surface 523 and ribs 524 of stuffing box 520 via stationary ring 360 . Therefore, at room temperature, the force ring 350 and the stationary ring 360 transmit substantially the axial pressure from the stuffing box 520 associated with the coupling between the stuffing box 520 and the gland 530 to the V-packing 120 . This axially compresses the V-packing 120 and raises the sealing pressure to the desired height. On the other hand, at low temperatures, the pressing ring 350 tightens the stationary ring 360 by thermal contraction, and the pressing ring 350 presses the male adapter 370 in the axial direction due to the corresponding reaction force PR from the stationary ring 360 . Since the V-packing 120 is further compressed in the axial direction by this pressure PB to increase the stress in the radial direction, the sealing pressure of the V-packing 120 is maintained sufficiently high regardless of the temperature drop. In this way, the shaft seal 300 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.

Like the V-packing 120, the pressing ring 350 is also made of fluororesin, so the heat shrinkage rate of the pressing ring 350 is equal to or higher than that of the V-packing 120. FIG. As a result, the pressure PB associated with the thermal contraction of the pressing ring 350 increases as the thermal contraction of the V-packing 120 increases significantly. Therefore, it is possible to effectively prevent the sealing pressure of the V-packing 120 from decreasing as the temperature drops.

Since the stationary ring 360 is made of metal, the tapered outer peripheral surface 361 has high rigidity against the pressure PA received from the tapered inner peripheral surface 352 of the pressing ring 350, and does not substantially deform under the pressure PA. Therefore, since the tapered inner peripheral surface 352 can smoothly slide along the tapered outer peripheral surface 361 , the pressure PA from the tapered inner peripheral surface 352 can be efficiently converted into the axial pressure PB to the V-packing 120 .

A pressing ring 350 and a stationary ring 360 are located on the lips 122 , 123 side of each V ring 121 . Therefore, the axial pressure PB of the pressing ring 350, which rises as the temperature drops, causes the lips 122 and 123 of the V-ring 121 to open further, causing the outer peripheral surface 511 of the stem 510 and the inner peripheral surface 523 of the stuffing box 520 to open. Press harder. As a result, the sealing performance of the V-packing 120 at low temperatures is even higher.

The pressing ring 350 and the stationary ring 360 are located on the opposite side of the V-packing 120 from the packing retainer 530 . In this case, the pressure PB of the pressing ring 350, which rises as the temperature drops, reaches the packing gland 530 after being weakened by the friction between each V-ring 121 and its surroundings 510, 110. FIG. Therefore, it is unlikely that the bolt 534 will loosen due to the pressure PB from the pressing ring 350, so the packing gland 530 can return a sufficiently strong reaction force against 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 the sealing pressure is maintained sufficiently high.
[Modification]

The second embodiment can also be modified in the same manner as the first embodiment. Also, if the compression ring 350 is sufficiently rigid, the male adapter 370 can be removed and instead the air side end (the left end in FIG. 5) of the compression ring 350 is the most fluid side (the rightmost in FIG. 5). may directly contact the V-ring 121 of

100 Shaft seal 120 Packing 121 V-ring 122 Inner lip 123 Outer lip 124 Heel 140 Female adapter 141 Annular surface on the atmosphere side of the female adapter 142 Concavity on the fluid side of the female adapter 150 Pressing ring 151 Convex on the atmosphere side of the pressing ring Portion 152 Taper outer peripheral surface of pressing ring 160 Clamping ring 161 Tapered inner peripheral surface of clamping ring 162 Fluid-side annular surface of clamping ring 510 Stem 511 Stem outer peripheral surface 520 Stuffing box 521 Fluid-side end of stuffing box Portion 522 Air side end of stuffing box 523 Stuffing box inner peripheral surface 524 Rib 525 Air side annular surface of rib 530 Packing gland 531 Fluid side end of packing gland 532 Air side end of packing gland 533 Flange 534 Bolt 535 Nut 540 Flow path 550 Casing 551 Casing opening 560 Casing external space

Claims (4)

A shaft seal for sealing a gap between a movable shaft of a fluid device and a stuffing box,
a resin packing that fills the gap with axial pressure from a packing retainer;
A support body, which is an annular structure surrounding the movable shaft and has one side in the axial direction in contact with one end in the axial direction of the packing and the other side in contact with the stuffing box or the packing retainer,
at least a part of the support in the axial direction,
The outer peripheral side has a higher thermal contraction rate than the inner peripheral side, and includes a tightening region where the outer peripheral side tightens the inner peripheral side as the temperature drops,
A shaft seal, wherein the support body is configured such that a force with which the outer peripheral side tightens the inner peripheral side is transmitted from the tightening region to the packing in the axial direction. The support is
a tightening ring that is an annular member that surrounds the movable shaft and includes a tapered inner peripheral surface that is inclined toward the packing in the axial direction so that the diameter narrows from the end to the center in the axial direction;
An annular member that surrounds the movable shaft, has a lower heat shrinkage than the tightening ring, and is slanted away from the packing in the axial direction so that the diameter narrows from the center toward the end in the axial direction. a pressing ring including a tapered outer peripheral surface;
In the tightening region, the tapered inner peripheral surface contacts the tapered outer peripheral surface,
A shaft seal according to claim 1. The support is
a pressing ring, which is an annular member surrounding the movable shaft and which includes a tapered inner peripheral surface inclined in the axial direction away from the packing so that the diameter increases from the center toward the end in the axial direction;
An annular member surrounding the movable shaft, having a lower thermal contraction rate than the pressing ring, and tapered toward the side close to the packing in the axial direction so that the diameter increases from the end to the center in the axial direction. a stationary ring including an outer peripheral surface;
In the tightening region, the tapered inner peripheral surface contacts the tapered outer peripheral surface,
A shaft seal according to claim 1. The packing is a V-packing,
The support is
Having a male adapter that contacts one end in the axial direction of the packing,
A shaft seal according to claim 2 or 3.

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