JP2023100138A - gland packing - Google Patents

Abstract

To suppress occurrence of penetration leakage in a gland packing having a spiral structure.SOLUTION: A gland packing (1) is compressed and molded into a cylindrical shape by winding a string-like body (3), which is formed by braiding a yarn (5), into a helical shape. A leakage prevention sheet (11) having a fluid penetration rate, which is lower than that of the string-like body (3), is interposed between the string-like bodies (3) adjacent to each other in an axial direction (Da) along a helical center of the string-like body (3).SELECTED DRAWING: Figure 2

Description

The present disclosure relates to gland packing.

2. Description of the Related Art Conventionally, gland packing has been used in fluid devices such as pumps and valves in order to prevent pressurized fluid from flowing out of the device. The gland packing is packed in a stuffing box at a portion of the fluid device through which the movable shaft passes, and is arranged around the movable shaft. A known gland packing has a spiral structure in which a cord-like body is spirally wound and integrally molded for ease of handling (see, for example, Patent Document 1).

JP 2006-349147 A

In the gland packing described above, the string-like body is formed by braiding fibrous materials such as carbon fibers and aramid fibers, and has gaps between the fibrous materials. The fluid pressurized by the fluid device penetrates into the gaps between the fibrous materials. Therefore, in the gland packing, permeation leakage occurs in which the fluid passes through the string-shaped body in the axial direction of the movable shaft.

An object of the present disclosure is to suppress the occurrence of permeation leakage in a gland packing having a spiral structure.

The technique of the present disclosure is directed to a gland packing formed into a tubular shape by spirally winding a string-like body containing a fibrous material. In the gland packing according to the technology of the present disclosure, a leakage prevention sheet having a lower fluid permeability than the string-shaped body is interposed between the string-shaped bodies that are adjacent to each other in the axial direction along the spiral center of the string-shaped body. do.

In this configuration, the leakage prevention sheet is interposed between the string-shaped bodies adjacent to each other. The fluid permeability in the leak-proof sheet is lower than the fluid permeability in the cord-like body. Therefore, even if the fluid permeates through the gaps between the fibrous materials forming the string-like body, the leakage prevention sheet can prevent the permeation of the fluid from moving between the adjacent string-like bodies toward the outside of the fluid device. .

According to the technique of the present disclosure, it is possible to suppress permeation leakage from occurring in the gland packing having a spiral structure.

FIG. 1 is a cross-sectional view illustrating a schematic configuration of a shaft seal portion in which a gland packing of a fluid device is used. FIG. 2 is a perspective view illustrating a gland packing. FIG. 3 is a perspective view exemplifying a string-like body and a leakage prevention sheet that constitute the gland packing. FIG. 4 is a cross-sectional perspective view illustrating a string-like body that constitutes the gland packing. FIG. 5A is a cross-sectional view illustrating a state during molding in manufacturing the gland packing. FIG. 5B is a cross-sectional view illustrating a state during molding in manufacturing the gland packing.

Exemplary embodiments are described in detail below on the basis of the drawings. The drawings are for conceptually explaining the present disclosure. Therefore, in the drawings, dimensions, ratios, or numbers may be exaggerated or simplified in order to facilitate understanding of the technology of the present disclosure.

The gland packing 1 of this embodiment is a sealing material that prevents fluid such as liquid and gas from leaking out from pumps such as rotary pumps and reciprocating pumps, valves such as cast iron valves, and various fluid devices 100 such as stirrers. used as

As shown in FIG. 1 , the fluidic device 100 includes a stuffing box 101 , a movable shaft 102 and a packing retainer (ground) 103 . A movable shaft 102 is inserted through the stuffing box 101 . The movable shaft 102 is a shaft member that performs rotational motion around the center line CL, reciprocating motion in the axial direction Da, or helical motion. An annular space S is formed between the inner peripheral surface of the stuffing box 101 and the outer peripheral surface of the movable shaft 102 .

The gland packing 1 is loaded into the annular space S thereof. The gland packing 1 is arranged around the movable shaft 102 . The gland packing 1 is packed in the axial direction Da by a packing retainer 103 arranged outside the stuffing box 101 . When the gland packing 1 is compressed and crushed by the packing retainer 103 , it comes into surface contact with the inner peripheral surface of the stuffing box 101 and the outer peripheral surface of the movable shaft 102 .

The gland packing 1 seals the fluid handled by the fluid device 100 while permitting the motion of the movable shaft 102 (rotational motion, reciprocating motion, or helical motion). The packing retainer 103 is fastened to the stuffing box 101 with bolts 104 . The frictional resistance (frictional force) between the inner peripheral surface of the gland packing 1 and the outer peripheral surface of the movable shaft 102 is adjusted by adjusting the tightness of the packing retainer 103 .

- Configuration of Gland Packing -
As shown in FIG. 2, the gland packing 1 is a packing having a spiral structure. The gland packing 1 of this example is a kind of blade packing (braided packing). The gland packing 1 is constructed as an integrally molded product in which a string-like body 3 containing a fibrous material is spirally wound and molded into a cylindrical shape. The gland packing 1 requires a relatively short production lead time and is excellent in handleability as compared with a gland packing formed by combining a plurality of types of packing parts.

As shown in FIG. 3, the string-like body 3 is a single continuous elongated object. Both ends of the string-like body 3 each have an inclined end face 7 forming a cut end. As shown in FIG. 2 , each inclined end surface 7 is inclined with respect to the axial direction Da along the spiral center of the string-like body 3 so as to face the inner side of the axial direction Da. The inclined end surfaces 7 at both ends of the string-like body 3 are in a corresponding positional relationship in the axial direction Da in the circumferential direction Dc of the gland packing 1 . The length of the string-like body 3 is set according to the number of turns of the string-like body 3 so that the inclined end surfaces 7 have the positional relationship described above.

The number of windings (the number of layers) of the string-like body 3 depends on the depth of the annular space S of the stuffing box 101 of interest, and is, for example, 5 times or more and 10 times or less. The gland packing 1 having a helically wound spiral structure functions like a compression coil spring, and a restoring force in the axial direction Da against the tightening pressure of the packing retainer 103 is obtained. As a result, it is possible to reduce the decrease in tightening pressure on the gland packing 1 due to stress relaxation. This is advantageous for maintaining the sealing performance of the gland packing 1 over a long period of time.

The angle α between each inclined end surface 7 of the string-like body 3 and the length direction Dl of the string-like body 3 is set in consideration of the integral molding property and the restoring property of the gland packing 1 . The angle α of the inclined end face 7 is the angle formed inside the string-like body 3 . As the angle α of the inclined end surface 7 approaches a right angle (90°), the inclination of the spiral formed by the string-like body 3 increases, the amount of bending of the gland packing 1 increases, and the resilience of the spiral structure increases. On the other hand, the farther the angle α of the inclined end surface 7 is from the right angle (90°), the easier it is to form the end surface of the gland packing 1 flat and to ensure the sealing performance.

From the above, it is preferable that the angle α of each inclined end surface 7 is 65° or more and 75° or less. When the angle α of the inclined end face 7 is less than 65°, the restoring force obtained in the gland packing 1 against the tightening pressure of the packing retainer 103 is relatively small. When the angle α of the inclined end face 7 exceeds 75°, gaps are likely to be formed in the joint portion 9 between the both end portions of the string-like body 3 and the portion facing the inclined end face 7 in the gland packing 1, thereby degrading the sealing performance. may cause

As shown in FIG. 4, the cord-like body 3 of this example is a braided product obtained by braiding a plurality of knitting threads (yarns) 5 into a rectangular cross section. The knitting yarn 5 is an example of a fibrous material. For example, the yarn 5 is braided in an eight-ply braid. The knitting yarn 5 may be braided by other knitting methods such as bag knitting and lattice knitting. The string-like body 3 may be provided with a core material, and the knitting yarn 5 may be braided around the core material. A gap is formed between the knitting yarns 5 forming the string-like body 3 . The fluid pressurized by the fluid device 100 permeates this gap.

Expanded graphite thread is used as the knitting thread 5 . The expanded graphite thread is a linear body obtained by folding expanded graphite tape, a linear body obtained by laminating expanded graphite tape on a metal foil or the like, or a high-strength fiber such as a metal wire and the expanded graphite thread. It is a filamentous body obtained by spirally winding or twisting a tape. Expanded graphite is excellent in heat resistance, compressive strength, chemical resistance, corrosion resistance, and self-lubricating properties, and is highly flexible and elastic, so it is suitable as a material for the gland packing 1 .

The expanded graphite thread is reinforced with a reinforcing wire. An organic fiber is used for the reinforcing wire rod of this example. Examples of organic fibers include cotton, rayon, phenol fiber, aramid fiber, PBI (Polybenzimidazole) fiber, PBO (Poly p-phenylenebenzobisoxazole) fiber, PTFE (Polytetrafluoroethylene) fiber, PPS (Poly phenylene sulfide) fiber, PEEK (Poly ether ether ketone) fibers and the like.

The string-like body 3 is provided with resin particles and impregnated with oil for the purpose of improving slidability and sealing performance. The resin particles are made of, for example, fluororesin. The resin particles of this example are PTFE particles made of PTFE. The resin particles may be composed of other fluororesins such as FEP (fluorinated ethylene-propylene copolymer) and PFA (Perfluoroalkoxy alkane). Silicone oil, for example, is used as the oil.

As shown in FIG. 2 , the gland packing 1 has a leakage prevention sheet 11 . The leak-preventing sheet 11 is a member having lower fluid permeability than the string-like body 3 . The “fluid” referred to here is the fluid handled by the fluid device 100 in which the gland packing 1 is used. The leakage prevention sheet 11 is interposed between the string-like bodies 3 adjacent to each other in the axial direction Da of the string-like bodies 3 . The leak-preventing sheet 11 is provided on one surface (the upper surface in FIG. 2) of the string-like body 3 in the axial direction Da, and is provided on the other surface (the lower side in FIG. 2) of the string-like body 3 in the axial direction Da. surface).

As shown in FIG. 3 , the leakage prevention sheet 11 is adhered to one side surface of the string-like body 3 before being formed into a tubular shape, and is attached over the entire length of the string-like body 3 . As shown in FIG. 2, the surface of the leakage prevention sheet 11 opposite to the adhesive side is joined to the opposite surface of the cord-like body 3 during compression molding of the gland packing 1, which will be described later. Thus, only one layer of the leakage prevention sheet 11 is interposed between the adjacent string-like bodies 3 . The leakage prevention sheet 11 is provided on one end face of the gland packing 1 (the upper end face in FIG. 2), but not on the other end face of the gland packing 1 (the lower end face in FIG. 2). .

An expanded graphite sheet is used for the leakage prevention sheet 11 of this example. The expanded graphite sheet is obtained by rolling expanded graphite into a sheet. The expanded graphite sheet is suitable as the leakage prevention sheet 11 because it has the properties of the expanded graphite described above and has low permeability to fluids such as liquids and gases. The leak-preventing sheet 11 is made of expanded graphite in common with the string-like body 3 . Therefore, the leak-preventing sheet 11 and the string-like body 3 have good mutual affinity, and when the gland packing 1 is compression-molded, the contact surfaces of the sheet and the string-like body 3 are firmly joined together. The thickness of the leakage prevention sheet 11 is, for example, 0.3 mm or more and 0.5 mm or less.

－Manufacturing method of gland packing－
In order to manufacture the gland packing 1 having the above structure, first, an expanded graphite yarn reinforced with a reinforcing wire (organic fiber) is prepared as the knitting yarn 5, and the expanded graphite yarn is knitted in an octagon, a bag, or a grid. A long cord-like body 3 is produced by braiding by a known weaving method. Next, the string-like body 3 is immersed in a suspension in which a dispersion containing resin particles such as PTFE particles and an oil such as silicone oil are mixed, and is pulled out after a predetermined period of time. The string-like body 3 is then impregnated with the dispersion and the oil.

At this time, if the impregnation amount of the dispersion and oil is less than 40% by mass with respect to 100 parts by mass of the string-like body 3, the bondability between the string-like body 3 and the leakage prevention sheet 11 is reduced, and the gland packing 1 is difficult to form as an integrally molded product. Further, if the impregnated amount of the dispersion and oil exceeds 70% by mass with respect to 100 parts by mass of the string-like body 3, the basic performance of the gland packing 1 is likely to be impaired. For these reasons, the impregnated amount of the dispersion and oil is 40 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the string-like body 3, that is, the impregnation rate is 40% or more and 60% or less. is preferred.

Subsequently, the string-like body 3 impregnated with the dispersion and oil is dried. After that, the string-like body 3 is cut to a required length, and inclined end faces 7 having a predetermined angle α are formed on both end faces of the string-like body 3 . Next, a leak prevention sheet 11 is provided on one side surface of the string-like body 3 . The leak prevention sheet 11 is prepared in advance by this stage. One side surface of the leakage prevention sheet 11 is an adhesive surface having adhesiveness like an adhesive tape. The leakage prevention sheet 11 is adhered to the string-like body 3 by applying an adhesive surface to the surface of the string-like body 3 and sticking it.

Next, the string-like body 3 with the leakage prevention sheet 11 is press-molded into a cylinder. In press molding, for example, a mold 200 shown in FIGS. 5A and 5B is used. The mold 200 includes a disk-shaped bottom mold 201 , a cylindrical outer mold 202 , a cylindrical core mold 203 and a cylindrical pressing mold 207 . The bottom mold 201 , the outer mold 202 and the core mold 203 are combined together to form a holding mold 205 . The holding mold 205 forms an annular concave portion 209 (cavity) in plan view.

In the process of forming the gland packing 1, as shown in FIG. 5A, the string-like body 3 with the leakage prevention sheet 11 is spirally wound and set in the recess 109 of the holding mold. At this time, the string-like body 3 is wound so that the inclined end surfaces 7 at both ends thereof come to corresponding positions in the circumferential direction Dc. A leak-preventing sheet 11 is arranged between portions of the spirally wound string-like body 3 that are adjacent in the axial direction Da. In this state, as shown in FIG. 5B, the pressing die 207 is inserted into the recess 209 of the holding die 205 to press the string-like body 3 with the leakage prevention sheet 11 set in the recess 209 . Then, the string-like body 3 and the leakage prevention sheet 11 are integrally joined to form the gland packing 1. - 特許庁

Thus, the gland packing 1 can be manufactured.

- Features of the embodiment -
In the gland packing 1 of this embodiment, the leakage prevention sheet 11 is interposed between the string-like bodies 3 adjacent to each other. The fluid permeability of the leak-preventing sheet 11 is lower than the fluid permeability of the string-like body 3 . Therefore, even if the fluid permeates through the gaps between the fibrous materials (knitting yarns 5) forming the string-like body 3, the permeation of the fluid moves between the adjacent string-like bodies 3 toward the outside of the fluid device 100. can be blocked by the leakage prevention sheet 11. Therefore, it is possible to suppress permeation leakage from occurring in the gland packing 1 having a spiral structure.

In the gland packing 1 of this embodiment, both ends of the string-like body 3 have inclined end surfaces 7 respectively. The angle α of each inclined end surface 7 is 65° or more. As a result, the restoring force obtained in the gland packing 1 against the tightening pressure by the packing retainer 103 is relatively large. As a result, it is possible to effectively reduce the reduction in tightening pressure on the gland packing 1 due to stress relaxation. Also, the angle α of each inclined end face 7 is 75° or less. As a result, in the gland packing 1 , it is possible to suppress the formation of a gap at the joint portion 9 between the both end portions of the string-like body 3 and the portion facing the inclined end surface 7 . This is advantageous for ensuring the sealing performance of the gland packing 1.

In the gland packing 1 of this embodiment, an expanded graphite sheet is used as the leakage prevention sheet 11 . An expanded graphite sheet is suitable for the leak prevention sheet 11 because of its properties. Therefore, the expanded graphite sheet is useful for specific realization of the gland packing 1 capable of suppressing permeation leakage of the fluid handled by the fluid device 100 .

In the gland packing 1 of this embodiment, the string-like body 3 is a braid made by braiding the knitting yarn 5 . Expanded graphite thread is used for the knitting thread 5 . Since the string-like body 3 is made of the same material (expanded graphite) as the leak-preventing sheet 11, the string-like body 3 and the leak-preventing sheet 11 can be firmly joined when the gland packing 1 is press-molded. Thereby, the gland packing 1 can be manufactured as an integrally molded product. Such an integrally molded gland packing 1 is relatively easy to load and remove from the stuffing box 101, and is excellent in handleability.

In the gland packing 1 of this embodiment, the leakage prevention sheet 11 is provided on one side surface of the string-like body 3 in the axial direction Da, and is joined to the other side surface of the string-like body 3 in the axial direction Da. When the leak-preventing sheet 11 is provided on only one side surface of the string-like body 3 in this way, when the string-like body 3 with the leak-preventing sheet 11 is press-molded, the leakage-preventing sheet 11 and the string-like body 3 are in good condition. is spliced to Therefore, the gland packing 1 can easily be made into an integrally molded product that is excellent in handleability and the like.

As described above, preferred embodiments have been described as illustrations of the technology of the present disclosure. However, the technology of the present disclosure is not limited to this, and can also be applied to embodiments in which changes, replacements, additions, omissions, etc. are made as appropriate. It should be understood by those skilled in the art that the above embodiment can be further modified in various ways without departing from the scope of the technology of the present disclosure, and that such modifications also belong to the scope of the technology of the present disclosure.

For example, the leakage prevention sheet 11 may be provided on both sides of the string-like body 3 in the axial direction Da. In this case, in manufacturing the gland packing 1, when the string-like body 3 with the leakage prevention sheet 11 is press-molded, the leakage prevention sheets 11 are joined together. Therefore, the surface of the leak-preventing sheet 11 may be subjected to a surface treatment to improve the bondability.

As the leakage prevention sheet 11, a material other than the expanded graphite sheet, such as a PTFE sheet made of PTFE, may be used as long as it can be well bonded to the string-like body 3 by press molding.

The string-like body 3 is not limited to a braided body. The string-like body 3 may be configured by twisting a plurality of knitting yarns 5 in a bundled state. The string-like body 3 may have another configuration such as a configuration in which a core material is provided and the knitting yarn 5 is twisted around the core material. Any configuration can be adopted for the string-like body 3 as long as it contains a fibrous material that forms gaps through which fluid can permeate.

The knitting yarn 5 is not limited to expanded graphite yarn, and may be other inorganic fibers, organic fibers, or metal wires. Examples of inorganic fibers include carbon fibers, ceramic fibers, and glass fibers. Organic fibers include, for example, cotton, rayon, phenol fiber, aramid fiber, PBI fiber, PBO fiber, PTFE fiber, PPS fiber, and PEEK fiber. Metal wires include, for example, stainless steel wires, Inconel wires, and Monel wires. The reinforcing wire is not limited to organic fibers, and may be inorganic fibers or metal wires as described above.

As described above, the technique of the present disclosure is useful for gland packing.

α Angle of inclined end surface Da Axial direction 1 Gland packing 3 String-like body 5 Braided yarn 7 Inclined end surface 11 Leakage prevention sheet

Claims (5)

A gland packing formed into a cylindrical shape by spirally winding a string-like body containing a fibrous material,
Between the string-shaped bodies adjacent to each other in the axial direction along the spiral center of the string-shaped body, a leakage prevention sheet having a lower fluid permeability than the string-shaped body is interposed.
ground packing. In the gland packing according to claim 1,
Both ends of the string-shaped body each have an inclined end face inclined to face the inside in the axial direction with respect to the axial direction,
The angle formed between the inclined end face and the length direction of the string-like body is 65° or more and 75° or less.
ground packing. In the gland packing according to claim 1 or 2,
An expanded graphite sheet is used for the leakage prevention sheet,
ground packing. In the gland packing according to any one of claims 1 to 3,
The string-like body is a braided product obtained by braiding the knitting yarn as the fibrous material,
Expanded graphite yarn is used for the knitting yarn,
ground packing. In the gland packing according to any one of claims 1 to 4,
The leakage prevention sheet is provided on one surface of the string-shaped body in the axial direction and is joined to the other surface of the string-shaped body in the axial direction.
ground packing.